Biological agent-exosome compositions and uses thereof

ABSTRACT

The present invention relates to compositions comprising exosomes and biological agents and methods of using the compositions for the delivery of biological agents to cells and to subjects.

STATEMENT OF PRIORITY

This application is a continuation application of and claims priority toU.S. patent application Ser. No. 16/089,833, filed Sep. 28, 2018, whichis a 35 U.S.C. § 371 national phase application of PCT/US2017/024931,filed Mar. 30, 2017, which claims the benefit of U.S. ProvisionalApplication Ser. No. 62/315,389, filed Mar. 30, 2016, the entirecontents of each of which are incorporated by reference herein.

STATEMENT OF GOVERNMENT SUPPORT

This invention was made with government support under Grant No. NS057748awarded by National Institutes of Health. The government has certainrights to this invention.

FIELD OF THE INVENTION

The present invention relates to compositions comprising exosomes andbiological agents and methods of using the compositions for the deliveryof biological agents to cells and to subjects.

BACKGROUND OF THE INVENTION

The delivery of biological agents to cells and tissues is hindered by anumber of factors, including the instability of administeredmacromolecule agents in vivo, sequestration by tissues, the presence ofthe blood-brain barrier (BBB), and brain-to-blood efflux systems.Different drug nanoformulations have been developed to overcome the BBB.Unfortunately, the opsonization of drug-loaded nanoparticles in thebloodstream caused two main problems of drug nanoformulations:nanotoxicity and rapid drug clearance by the mononuclear phagocytesystem (MPS).

Exosomes are nanosized vesicles secreted by a variety of cells, inparticular cells of the immune system (Vlassov et al., Biochem. Biophys.Acta 1820:940 (2012)). Exosomes may have an immune-privileged statusthat can efficiently decrease drug clearance. Exosomes were initiallythought to be a mechanism for removing unneeded proteins. Recent studiesrevealed that they are actually specialized in long-distanceintercellular communications facilitating transfer of proteins(Johnstone, Biochem. Cell Biol. 70:179 (1992)), functional mRNAs andmicroRNAs for subsequent protein expression in target cells (Zomer etal., Commun. Integr. Biol. 3:447 (2010); Valadi et al., Nature CellBiol. 9:654 (2007)). To shuttle their cargo, exosomes can attach by arange of surface adhesion proteins and specific vector ligands(tetraspanins, integrins, CD11b and CD18 receptors), and deliver theirpayload to target cells (Thery et al., Curr. Protoc. Cell Biol. Chapter3, Unit 3 22 (2006); Thery et al., Nature Rev. Immunol. 9:581 (2009)).Exosomes possess an intrinsic ability to cross biological barriers.Thus, tumor-derived exosomes and microvesicles originated in the brainof glioma-bearing mice, and human glioblastoma patients were detected inthe blood circulation indicating their ability to cross the BBB (Skog etal., Nature Cell Biol. 10:1470 (2008)).

There is a need in the art for new compositions and methods for thedelivery of biological agents to cells and to subjects.

SUMMARY OF THE INVENTION

The present invention is based on the development of compositions usefulfor delivering biological agents, e.g., therapeutic or protective agentssuch as small molecules, polypeptides, and polynucleotides, to cells invitro and in vivo. The compositions provide improved delivery ofbiological agents, including crossing the BBB to the brain, andtargeting inflamed tissues and tumors, thereby improving therapeuticeffects while limiting immune response to the agents. The incorporationof biological agents into exosomes increases the circulation time,preserves therapeutic activity, and improves delivery to the centralnervous system, the tumor microenvironment, and inflamed tissue. Theexosomes enable intracellular delivery of the loaded biological agentsto target cells such as cancer cells, muscle cells, brain cells, cellsof the immune system, and the like. The exosomes can optionally bemodified to increase loading of biological agents in these exosomes,and/or to enable targeting of the exosomes to the specific receptor atthe surface of a target cell.

Thus, one aspect of the invention relates to a composition for deliveryof a biological agent to a cell, the composition comprising an exosomecomprising the biological agent, wherein the biological agent is notnaturally present in the exosome. The exosomes may be isolated fromdonor cells such as cancer cells, immune cells, such asmacrophages/monocytes or dendritic cells, or stem cells. The biologicalagent may be incorporated in the exosomes prior to or after isolation ofthe exosomes from the cells.

Another aspect of the invention relates to a method of delivering abiological agent to a cell, comprising contacting the cell with thecomposition of the invention, thereby delivering the biological agent tothe cell.

A further aspect of the invention relates to a method of enhancingdelivery of a biological agent to a cell in a tumor microenvironment,comprising contacting the cell with the composition of the invention,thereby enhancing delivery of the biological agent to the cell relativeto the delivery of the biological agent in the absence of an exosome.

An additional aspect of the invention relates to a method of enhancingdelivery of a biological agent to a cell in a tumor microenvironment,comprising contacting the cell with the composition of the invention,thereby enhancing delivery of the biological agent to the cell relativeto the delivery of the biological agent in the absence of an exosome.

Another aspect of the invention relates to a method of enhancingdelivery of a biological agent to a cancer cell, comprising contactingthe cell with the composition of the invention, thereby enhancingdelivery of the biological agent to the cell relative to the delivery ofthe biological agent in the absence of an exosome.

A further aspect of the invention relates to a method of enhancingdelivery of a biological agent to a central nervous system cell,comprising contacting the cell with the composition of the invention,thereby enhancing delivery of the biological agent to the cell relativeto the delivery of the biological agent in the absence of an exosome.

An additional aspect of the invention relates to a method of deliveringa biological agent to a subject, comprising delivering the compositionof the invention to the subject, thereby delivering the biological agentto the subject.

Another aspect of the invention relates to a method of delivering abiological agent across the BBB of a subject, comprising delivering thecomposition of the invention to the subject, thereby delivering thebiological agent across the BBB of the subject.

A further aspect of the invention relates to a method of delivering abiological agent to inflamed tissue of a subject, comprising deliveringthe composition of the invention to the subject, thereby delivering thebiological agent to inflamed tissue of the subject.

A further aspect of the invention relates to a method and compositionsof exosomes for delivering polypeptides not naturally present in theexosomes.

A further aspect of the invention relates to a method and compositionsof exosomes for delivering functional polynucleotides not naturallypresent in the exosomes.

A further aspect of the invention relates to a method and compositionsof exosomes for delivering small molecules not naturally present in theexosomes.

Another aspect of this invention relates to a method of increasing thedelivery of the exosomes to the target cells and organs such as cancercells or tumor microenvironment and compositions in which the exosomesoptionally carrying a biological agent are modified with the targetinggroups. These targeting groups can be attached to the surface ofexosomes using a polymeric linker that can be connected to a lipidgroup.

An additional aspect of the invention relates to a method of treating adisorder in a subject in need thereof, comprising delivering atherapeutically effective amount of the composition of the invention tothe subject, wherein the biological agent is effective for treating thedisorder, thereby treating the disorder in the subject.

Another aspect of the invention relates to a method of transfecting acell with a polynucleotide, comprising contacting the cell withcomposition comprising an exosome comprising the polynucleotide, whereinthe polynucleotide is not naturally present in the exosome. The exosomesmay be isolated from donor mammalian cells, in particular, cancer cells,immune system cells, such as macrophages/monocytes or dendritic cells,or stem cells.

Another aspect of the invention relates to a method of increasingproduction of exosomes, comprising treating the donor cells withamphiphilic block copolymers that may be applied before and/or duringisolation of the exosomes.

A further aspect of the invention relates to a method of loading abiological agent into an exosome, comprising a step selected from thegroup consisting of:

a) incubating the biological agent with the exosome, optionally in thepresence of a saponin;

b) combining the biological agent and the exosome and subjecting them toa freeze-thaw cycle;

c) combining the biological agent and the exosome and subjecting them tosonication;

d) combining the biological agent and the exosome and subjecting them toextrusion; and

e) modifying exosomes with a molecule containing multiple charges andoptionally purifying the exosomes before adding the biological agent.

Another aspect of the invention relates to compositions of exosomes inwhich exosomes are modified with molecules containing multiple chargesto increase incorporation of a biological agent into exosomes, and/orstability of the exosomes with the biological agent. The exosomes may bemodified with a polyion or a lipid that can contain multiple chargesthat can be either positive or negative charges. The exosomes modifiedwith a polyion or a lipid that can contain multiple charges may bepurified after modification. The modified exosomes may be then loadedwith a biological agent.

In another aspect this invention relates to a method of loading abiological agent into an exosome, comprising:

a) loading a donor cell with a biological agent that optionally can beincorporated into a nanoparticle comprising a polymer or a lipid, suchas polymeric micelle or a polyion complex;

b) culturing the cells to allow for formation of exosomes;

c) isolating exosomes loaded with the biological agent from these cells.

The cells may be optionally treated with a block copolymer to increasethe yield (amount) of exosomes loaded with a biological agent.

In another aspect this invention relates to a method of loading abiological agent into an exosome, comprising:

a) transfecting a donor cell with a polynucleotide that optionally canbe incorporated into a nanoparticle comprising a polymer or a lipid,such as a cationic polymer or a cationic lipid;

b) culturing the cells to allow for formation of exosomes;

c) isolating exosomes from these cells.

The cells may be optionally treated with a block copolymer to increasethe yield (amount) of exosomes. The isolated exosomes may carry the DNA,RNA and/or protein produced as a result of the transfection of the cellswith this polynucleotide.

These and other aspects of the invention are set forth in more detail inthe description of the invention below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-ID show characterization of exoCAT. Exosomes released from Raw264.7 macrophages were loaded with catalase by different techniques andexamined by: (FIG. 1A) western blot, (FIG. 1B) catalase enzymaticactivity; and (FIG. 1C) catalase release. ExoCAT morphology was examinedby AFM (FIG. 1D).

FIGS. 2A-2C show hyperspectral microscopy images of exoCAT formulation.Catalase was loaded into exosomes by sonication as described in Methodssection. The obtained exoCAT formulation (FIG. 2A) was examined byCytoViva nanoscale hyperspectral microscopy and compared to emptyexosomes (FIG. 2B). The spectral responses of the two samples (FIG. 2C)were quantitatively different showing narrowing of the spectral responseof the loaded exosomes versus the unloaded nanoparticles. Imagescaptured at 100× magnification.

FIG. 3 shows preservation of catalase enzymatic activity in exoCAT.ExoCAT obtained by sonication demonstrated the best protection ofcatalase.

FIGS. 4A-4D show accumulation of exoCAT in PC12 cells, and therapeuticeffects of exoCAT in in vitro models of oxidative stress. The exoCATuptake in PC12 cells was examined by spectrofluorimetry (FIG. 4A), andconfocal microscopy (FIG. 4B). The bar: 20 μm. The neuroprotection byexoCAT formulations was evaluated in the cell pre-incubated with 6-OHDA(FIG. 4C); (1) catalase, (2) empty exosomes, catalase loaded intoexosomes by: (3) incubation at RT, (4) saponin permeabilization, (5)freeze/thaw cycles, (6) sonication, (7) extrusion. The ability todecrease levels of ROS produced in activated macrophages (pre-incubatedwith LPS and TNF-α) by exoCAT was evaluated by Ampex Red assay in vitro(FIG. 4D).

FIGS. 5A-5D show biodistribution of DIL-labeled exosomes in mouse brain.Exosomes were administered to mice with 6-OHDA-induced braininflammation through: intranasal (FIG. 5A, FIG. 5B), or intravenous(FIG. 5C) routes; and compared to PBS-injected controls (FIG. 5D). Thebar: 40 μm.

FIGS. 6A-6G show anti-inflammatory effects of exoCAT in PD mouse model.The intranasal administration of exoCAT significantly decreasedmicroglial activation (FIG. 6D, FIG. 6E) in 6-OHDA-intoxicated micecompared to those intoxicated with 6-OHDA and then treated with PBS(FIG. 6C). Catalase alone did not decrease inflammation in PD mice (FIG.6F). Empty exosomes did not alter the microglial status in healthyanimals (FIG. 6B) compared to healthy controls (FIG. 6A). Theanti-inflammatory effects of the described exosomal formulations werequantified by the amount of activated microglial cells (FIG. 6G).

FIGS. 7A-7C show attenuation of astrocytosis in PD mice by exoCAT.6-OHDA-intoxicated mice were i.v. injected with PBS (FIG. 7B), or exoCAT(FIG. 7C). Mice treated with PBS in lieu of 6-OHDA served asnon-intoxicated controls (FIG. 7A). 21 days later animals weresacrificed, and brain tissues were subjected for confocal microscopywith staining for glial fibrillary acidic protein (GFAP). Representativeimages demonstrated decrease of neuroinflammation in animals treatedwith exoCAT (FIG. 7C) compared to PD mice treated with PBS (FIG. 7B).63× magnification.

FIGS. 8A-8G show neuroprotective effects of exoCAT in PD mouse model.The i.n. administration of exoCAT protected DA neurons (FIG. 8D, FIG.8E) in 6-OHDA-intoxicated mice compared to those intoxicated with 6-OHDAand then treated with PBS (FIG. 8C). Catalase alone was not efficient inthis model (FIG. 8F). Empty exosomes did not affect the number of DAneurons in healthy animals (FIG. 8B) compared to healthy controls (FIG.8A) indicating the absence of cytotoxic effects of the exosomalcarriers. The neuroprotective effects of the described exosomalformulations were quantified by the amount of DA neurons in the SNpc(FIG. 8G).

FIG. 9 shows the absence of toxic effect of exosomes released frommacrophages in primary neurons. Primary neurons were isolated from mousepups midbrain and cortex and cultured on 24-well plated for 24 hours. Inparallel, exosomes were isolated from BMM concomitant media, and addedto the neurons for 48 hours. Neurons incubated in the media withoutexosomes were used as controls. Following incubation, the cells werecollected and their survival was accounted by BSA method. No effect ofthe neuronal survival upon addition of exosomes was detected.

FIG. 10 shows co-localization of exosomes with different cells in themouse brain with inflammation. Exosomes released by BMM were labeledwith DIL (red). C57BL/6 mice were intoxicated with 6-OHDA, and then i.n.injected with fluorescently-labeled exosomes. Four hours later, micewere sacrificed, perfused, and brain slides were subjected for confocalexaminations. Brain slides were stained with antibodies to differentcell types and then secondary Ab 594. Nucleus was stained with DAPI.Bar: 10 μm.

FIG. 11 shows incorporation of gold nanoparticles into exosomes bysonication. Naïve exosomes isolated from macrophages concomitant mediawere sonicated in the presence of gold nanoparticles as described inmethods section and visualized by TEM. The bar: 100 nm.

FIGS. 12A-12E show characterization of PTX exosomal formulations.Exosomes were collected from conditioned media of RAW 264.7 macrophages,and loaded with PTX by various methods: co-incubation at RT;electroporation, and sonication. The size of exoPTX was measured by NTAand DLS (FIG. 12A). The loading with PTX increased the size of exosomes,but did not significantly altered their surface charge. The loadingefficiency of exosomes with PTX increased in a row: incubation atRT<electroporation <<sonication. The exosome protein content wasconfirmed by western blot (FIG. 12B). Significant amount ofexosome-associated proteins, Alix, TSG101, and Flotillin was detected innaïve (2) and sonicated exosomes (3), but not in the cells (1). Effectof sonication on fluidity of exosomal membranes labeled with BODIPY-PCwas examined by fluorescence polarization measurements (FIG. 12C). Themicroviscosity of exosomal membranes was significantly decreased by sixcycles of ultrasound treatment (3) compared to naïve exosomes (1), orexosomes subjected to one sonication cycle (2). The microviscosity ofsonicated exosomes was completely restored following one hour incubationperiod at 37 (5), but not after 30 min incubation (4). The morphology ofdrug-loaded exosomes was examined by AFM. (FIG. 12D). Images revealedsmall spherical naïve exosomes as well as PTX-loaded exosomes. The bar:200 nm. A release PTX profile from pre-loaded exosomes was evaluated forthe exoPTX formulation obtained by sonication (FIG. 12E). Values aremeans±SEM (n=4). Symbols indicate the relative level of significancecompared with naïve exosomes (p<0.05).

FIG. 13 shows the effect of sonication on fluidity of exosomalmembranes. Exosomes isolated from RAW 264.7 macrophages concomitantmedia were labeled with BODIPY-PC fluorescent dye as described inMethods section, and subjected to one or 6 cycles of ultrasoundtreatment. The fluorescence polarization was measured right after thesonication, or following 30 min or 1 hour incubation period at 37° C.Values are means±SEM (n=4). Symbols indicate the relative level ofsignificance compared with naive exosomes.

FIG. 14 shows the stability of exoPTX formulations. Exosomes releasedfrom Raw 264.7 macrophages were loaded with PTX as described in themethods section, and the size of nanoparticles was measured at 4° C.,RT, and 37° C. over the course of a month. No significant changes insize of the exoPTX were registered at all conditions.

FIGS. 15A-15B show a profound accumulation of exosomes in 3LL-M27 cellsin vitro. 3LL-M27 cells were incubated with fluorescently-labeled (red)exosomes, or liposomes, or PS NPs for various times and the amount ofaccumulated nanocarriers was examined by confocal microscopy (FIG. 15A),and spectrophotometry (FIG. 15B). Bar: 10 μm.

FIG. 16 shows exosomes do not inhibit Pgp-mediated drug efflux inresistant cancer cells. Resistant MDCK_(MDR1) cells and their sensitivecounterparts MDCK_(WT) were pretreated with verapamil, a well-known Pgpinhibitor, or empty exosomes, or media as a control. Then, cells weresupplemented with R123 solutions for two hours, washed, and accumulationof a Pgp substrate, R123, was examined by fluorescence. Verapamilsignificantly increased R123 accumulation in resistant cancer cells anddid not alter the R123 uptake in sensitive MDCK_(WT) cells. Contrary toverapamil, exosomes pretreatment did not affect accumulation levels ofR123 in resistant MDCK_(MDR1) cells, indicating that exosomes themselvesdid not inhibit Pgp efflux mechanism. Values are means±SEM (n=6).Symbols indicate the relative level of significance compared with R123uptake in verapamil or exosome-free media.

FIGS. 17A-17B show the effect of Pgp inhibition on DOX accumulation inMDR and sensitive cancer cells. The accumulation of free DOX or exoDOXin MDCK_(MDR1) and MDCK_(WT) cells was studied in cell lysates viawestern blot (FIG. 17A). The DOX incorporation into exosomessignificantly increased accumulation in sensitive and resistant cells,while no effect of verapamil on exoDOX accumulation was found in bothcell lines (FIG. 17B).

FIG. 18 shows R123 does not incorporate into exosomes upon incubation atRT. Exosomes (10¹¹ particles/ml) were supplemented with R123 solutionand incubated at RT as described in the methods section.Non-incorporated R123 was separated on from exosomes by size exclusionchromatography using a NAP-10 Sephadex® G25 column. Fractions werecollected from a column and analyzed by fluorescence (for R123) and NTA(for exosomes). The chromatography profile showed two separated peaks;the free R123 was expelled from the column at a much later time than theexosomes.

FIGS. 19A-19B show a lung metastasis model of Lewis Lung Carcinoma(3LL-M27). C57BL/6 mice were i.v. injected with 3LL/M27 cells. 21 daysfollowing the injection, multiple metastases (arrows) were detected ongross images of tumor-bearing lungs (FIG. 19A), and lung sections (FIG.19B).

FIGS. 20A-20C show co-localization of airway-delivered exoDOX withpulmonary metastases. Exosomes were isolated from macrophagesconditioned media, and loaded with DOX. C57BL/6 mice were i.v. injectedwith 3LL-M27 cells transduced with lentiviral vectors encoding theoptical reporter mCherry (8FlmC) fluorescent protein (FIG. 20A). 21 dayslater, the mice with established pulmonary metastases were i.n. injectedwith DID-labeled exosomes (FIG. 20B). 4 hours later, mice wereeuthanized, perfused, lungs were sectioned, and stained with DAPI. Theconfocal images revealed a significant co-localization ofexosome-delivered DOX with metastases (FIG. 20C). Bar: 20 μm.

FIGS. 21A-21B show co-localization of airway-delivered exosomes withpulmonary metastases. Exosomes were isolated from macrophagesconditioned media, and labeled with fluorescent dye, DID. C57BL/6 micewere i.v. injected with 3LL-M27 cells transduced with lentiviral vectorsencoding the optical reporter mCherry (8FlmC) fluorescent protein. 21days later, the mice with established pulmonary metastases were i.n.injected with DID-labeled exosomes. 4 hours later, mice were euthanized,perfused, lungs were sectioned, and stained with DAPI. The confocalimages revealed near complete co-localization of exosomes withmetastases. Images were obtained with ×10 (FIG. 21A), and ×60 (FIG. 21B)magnification. Bar: 50 μm.

FIGS. 22A-22C show the inhibition of metastases growth in mouse lungsupon exoPTX treatment. C57Bl/6 mice were i.v. injected with8FlmC-FLuc-3LL-M27 cells to establish pulmonary metastases. 48 hourlater mice were treated with exoPTX, or Taxol, or saline, or emptysonicated exosomes as a control, and the treatment was repeated everyother day, totally seven times. Representative IVIS images were taken atday 21 (FIG. 22A). Statistical significance of metastases levels fromIVIS images in lungs of treated animals compared to control mice isshown by asterisk (*p<0.05; **p<0.005) (FIG. 22B). At the endpoint, 21days later, mice were sacrificed, perfused, and lung slides wereexamined by confocal microscopy (FIG. 22C). The bar: 10 μm.

FIGS. 23A-23E show characterization of Mϕ exosomes. Exosomes werepurified by sequential centrifugation from RAW Mϕs conditioned medium.(FIG. 23A) Intensity-weighted size distribution of exosomes by DLS.(FIG. 23B) Number-weighted size distribution of exosomes by NTA. (FIG.23C) Morphology of Mϕ exosomes by TEM. Scale bar=200 nm,magnification×50,000. Insets show the aggregation and artificialcup-shape. (FIG. 23D) SDS-PAGE of lysates of RAW Mϕs and exosomes forprotein composition. (FIG. 23E) Western blot of lysates of RAW Mϕs andexosomes at equal protein amount for exosomal markers and conservedproteins.

FIGS. 24A-24B show (FIG. 24A) volume-weighted and (FIG. 24B)number-weighted diameter distribution of Mϕ exosomes by DLS.

FIGS. 25A-25D show uptake of Mϕ exosomes in hCMEC/D3 cells. (FIG. 25A)Cell viability of hCMEC/D3 cells after 24 h incubation with exosomes andanother 72 h in fresh culture medium was determined by MTT assay. Dataare means f SD, n=6. Cell viability of exosomes-treated cells wascomparable to untreated cells. (FIG. 25B) Time-dependent uptake ofCM-DiI labeled exosomes at 0.6×10¹⁰ exosomes/ml. *** p<0.001 vsuntreated cells. (FIG. 25C) Concentration-dependent uptake of CM-DiIlabeled exosomes at 4 h. *p<0.05 and ***p<0.001 vs untreated cells.(FIG. 25D) Concentration-dependent inhibition of non-labeled exosomes onuptake of CM-DiI labeled exosomes at 0.6×10¹⁰ exosomes/ml at 4 h. ***p<0.001 vs indicated group. Cell uptake was determined by flowcytometry. Data are mean fluorescence of 5000-10000 live singlets±SD,n=3. Statistical comparisons are made by one-way ANOVA and postNewman-Keuls multiple comparison test.

FIGS. 26A-26D show endocytosis pathways of Mϕ exosomes in hCMEC/D3cells. hCMEC/D3 cells were pre-incubated with endocytosis inhibitors for0.5 h, and then co-incubated with fresh inhibitors and (FIG. 26A) CM-DiIlabeled exosomes at 0.6×10¹⁰ exosomes/ml, (FIG. 26B) Alexa Fluor®488-transferin at 10 μg/ml, (FIG. 26C) Alexa Fluor® 488-CTB at 5 μg/ml,or (FIG. 26D) FITC-dextran (70 kDa) at 10 mg/ml for another 4 h. Allinhibitors at selected concentrations (except sucrose at 500 mM) ensuredat least 80% cell viability. Cell uptake was determined by flowcytometry. Data are mean fluorescence of 5000-10000 live singlets±SD,n=3. * p<0.05, ** p<0.01, and ***p<0.001 vs indicated group by one-wayANOVA and post Newman-Keuls multiple comparison test.

FIG. 27 shows charge saturation analysis by horizontal agaroseelectrophoresis.

FIGS. 28A-28B show laser scanning confocal microscopy (LSCM) of theuptake of Mϕ exosomes in hCMEC/D3 cells. (FIG. 28A) hCMEC/D3 cells weretreated with CM-DiI labeled exosomes at 1×10¹¹ exosomes/ml and AlexaFluor 488-transferrin at 25 μg/ml or Alexa Fluor 488-CTB at 5 μg/ml for0.5 h, and then fixed before imaging. (FIG. 28B) hCMEC/D3 cells weretreated with CM-DiI labeled exosomes at 1×10¹¹ exosomes/ml for 0.5 h,fixed and then immunostained with anti-clathrin heavy chain/-caveolin-1antibody. Mean±SD of Mander's colocalization coefficients calculated byImage J JACoP plugin (Schneider et al., Nature Methods 9:671 (2012);Bolte et al., J. Microsc.-Oxford 224:213 (2006)) from 7-30 differentfields of view are shown in percentage.

FIGS. 29A-29D show ICAM-1/LFA-1 mediated uptake of Mϕ exosomes inhCMEC/D3 cells. (FIG. 29A) Expression of LFA-1 in Raw Mϕs and Mϕexosomes by western blot at equal protein loading. (FIG. 29B) Expressionof ICAM-1 in hCMEC/D3 cells with or without 3 or 6 h stimulation withLPS (100 ng/ml). (FIG. 29C) Cell uptake of exosomes in hCMEC/D3 cellswith or without 3 or 6 h pre-stimulation with LPS. (FIG. 29D) Effect ofco-incubation with anti-ICAM-1 or anti-LFA-1 antibodies (100 μg/ml) oncell uptake of exosomes in hCMEC/D3 cells. Cell uptake was determined byflow cytometry after 4 h incubation with CM-DiI labeled exosomes at0.6×10¹⁰ exosomes/ml. Data are mean fluorescence of 5000-10000 livesinglets±SD, n=3. ** p<0.01 and ***p<0.001 vs indicated group by one-wayANOVA and post Newman-Keuls multiple comparison test.

FIGS. 30A-30C show C-type lectin receptors mediated the uptake of Mϕexosomes in hCMEC/D3 cells. (FIG. 30A) hCMEC/D3 cells were pre-incubatedwith carbohydrates for 0.5 h, and then co-incubated with exosomes for 4h. (FIG. 30B) hCMEC/D3 cells were co-incubated with EGTA and exosomesfor 4 h. (FIG. 30C) hCMEC/D3 cells were co-incubated with exosomes andDEC205 antibody at 100 μg/ml for 4 h. In all experiments, exosomes werelabeled with CM-DiI and used at 0.6×10¹⁰ exosomes/ml. The selectedconcentrations for carbohydrates and EGTA ensured at least 80% cellviability. Cell uptake of CM-DiI labeled exosomes was determined by flowcytometry. Data are mean fluorescence of 5000-10000 live singlets±SD,n=3. (FIG. 30A) The data was collected in two flow cytometry assays, andeach was normalized to cells treated with exosomes only. ***p<0.001 vsexosome only group (FIG. 30A) or indicated group (FIG. 30B, FIG. 30C) byone-way ANOVA and post Newman-Keuls multiple comparison test.

FIG. 31 shows the effect of glucose and glucosamine on ICAM-1 expressionin hCMEC/D3 cells. hCMEC/D3 cells were treated with glucose andglucosamine at indicated concentrations for 5 h. Protein expression wasdetermined by western blot using β-actin as loading control.

FIGS. 32A-32D show PK and biodistribution of Mϕ exosomes in healthy andbrain-inflamed CD-1 mice. The brain inflammation in CD-1 mice wasinduced by intracranial injection of 10 μg of LPS a day before study.The mice were injected with ¹²⁵I-labeled exosomes and ¹³¹I-labeled BSAvia jugular vein. (FIG. 32A) Serum clearance of exosomes and BSA inhealthy mice. n=1 per time point. (FIG. 32B) Biodistribution of exosomein healthy mice. (FIG. 32C) Multiple-time regression analysis ofexosomes for brain influx rate in healthy and brain-inflamed mice. Deltabrain/serum ratio was calculated by subtracting the brain/serum ratio ofBSA from that of exosomes to correct for vascular space (Banks et al.,Brain Behav. Immun. 24:102 (2010)). n=1 per time point. (FIG. 32D)Biodistribution of exosomes at 10 min. Tissue accumulation was correctedfor vascular space using BSA data. Data are means±SEM, n=3-6. #p<0.05,##p<0.01, and ###p<0.001 vs indicated group by unpaired two-tailedt-test.

FIGS. 33A-33C show the PK of Mϕ exosomes and BSA in healthy andbrain-inflamed CD-1 mice. The brain inflammation was induced byintracranial injection of 10 μg of LPS a day before study. The mice wereinjected with ¹²¹I-labeled Mϕ exosomes and ¹³¹I-labeled BSA via jugularvein. (FIG. 33A) Serum clearance of Mϕ exosomes and co-injected BSA. n=1per time point. (FIG. 33B) Plot of delta brain/serum ratio of Mϕexosomes against serum concentration of Mϕ exosomes. Delta brain/serumratio was calculated by subtracting the brain/serum ratio of BSA fromthat of exosomes to correct for vascular space (Banks et al., BrainBehav. Immun. 24:102 (2010)). (FIG. 33C) Multiple-time regressionanalysis of co-injected BSA for brain influx rate in healthy and braininflamed mice. n=1 per time point. Both slopes are comparable to zero.

FIGS. 34A-34B show the interaction between Mϕ exosomes and BDNF. (FIG.34A) BDNF loaded exosomes were isolated using protein G magnetic beadsmodified with BDNF-specific antibodies. (FIG. 34B) Native gelelectrophoresis of mixture of Mϕ exosomes and BDNF at different proteinratios.

FIGS. 35A-35C show brain delivery of BDNF and Mϕ exosomes complex.Healthy or brain-inflamed mice were co-injected with ¹³¹I-labeled BSAand ¹²¹I-labeled BDNF with or without Mϕ exosomes via jugular vein.(FIG. 35A) Plot of delta brain/serum ratio of BDNF vs exposure time inhealthy mice. Delta brain/serum ratio was calculated by subtracting thebrain/serum ratio of BSA from that of BDNF to correct for vascular space(Banks et al., Brain Behav. Immun. 24:102 (2010)), n=1 per time point.The two groups were compared by unpaired two-tailed t-test, ###p<0.001.(FIG. 35B) Multiple-time regression analysis of co-injected BSA inhealthy mice. Both slopes are comparable to 0 (p=0.064, 0.09 for BSA andBSA+Exosomes by unpaired two-tailed t-test, respectively). (FIG. 35C)Brain accumulation of naked or Mϕ exosomes formulated BDNF in healthy orbrain-inflamed mice at 10 min. The brain accumulation was corrected forvascular space using co-injected BSA data. Data are means±SEM, n=3,**p<0.01 indicated group by one-way ANOVA and post Newman-Keuls multiplecomparison test.

FIG. 36 shows transfection of RAW 264.7 macrophages with pDNAincorporated into exosomes. Various formulations of luciferase-encodingpDNA (2 μg/ml) were added to cell medium for 4 hours. Then, the cellswere cultured for additional 20 hours, and the expression of luciferasein cell lysates were assessed by luminescence.

FIG. 37 shows exosome-mediated delivery of pDNA into nuclei of targetcells. Model pDNA was labeled with fluorescent dye, YOYO, and formulatedinto exosomes. RAW 264.7 macrophages were incubated with exoDNA for 4hours, then cells were washed, permeabilized, nuclei—labeled with DAPI.Co-localization of pDNA and nuclei is evident in the images.

FIG. 38 shows optimization of exoDNA formulations. Various compositionsof exoDNA with different N/P ratio were prepared and examined for theirTransfection Efficacy in RAW 264.7 cells. The compositions with optimalN/P ratio (12) provided the best transfection efficacy.

FIG. 39 shows intracellular distribution of exosomes and GFP in targetcells. IC21 cells were transfected with optimal formulation GFP-encodingexoDNA formulation for 4 hours. Exosomes were labeled with DIL. Then,cells were permeabilized and nuclei—stained with DAPI. Expression of theencoded protein co-localized with exosomes was evident in the images.

FIG. 40 shows exosome-mediated delivery of siRNA into nuclei of targettriple negative breast cancer cells MDA-MB-468. Thefluorescently-labeled siRNA was formulated into the cationiclipid-modified exosomes. MDA-MB-468 cancer cells were incubated withexo-siRNA for 4 hours, then cells were washed with PBS, permeabilizedwith PFA, and nuclei were labeled with Hoechst nucleic acidcounterstain.

FIG. 41 shows the mean intensity of siRNA accumulation in MDA-MB-468cancer cells. The fluorescently-labeled siRNA was formulated into thecationic lipid-modified exosomes. MDA-MB-468 cancer cells were incubatedwith exo-siRNA for 4 hours, then cells were washed with PBS, andpermeabilized with PFA. The levels of siRNA accumulation in the cellswere analyzed by Image J software.

FIG. 42 shows transfection of Raw 264.7 macrophages withexosome-incorporated mRNA and pDNA. Luciferase-encoding mRNA or pDNAwere formulated into the cationic lipid-modified exosomes. The cellswere incubated with exo-mRNA or exo-pDNA, or control solutions (mRNA orpDNA formulated with GP3K; or naked mRNA or pDNA) for 4 hours, thencells were washed with PBS, and supplemented with full media for another24 hours. Following the incubation, the cells were lysed and theluciferase levels were determined using a luminometer.

FIGS. 43A-43C shows the effect of exosomes released fromGDNF-transfected macrophages on motor functions in ParkinQ311X(A)transgenic mice. IC21 macrophages were transfected with theGDNF-encoding pDNA, and exosomes released from GDNF-macrophages over 24hours to exosome-depleted serum media were harvested. Parkin Q311X(A)4-month-old mice were injected with exosomes collected fromGDNF-macrophages, or PBS as a control PD mice three times every week.Healthy wild type mice were injected with PBS in the same manner.Behavioral studies, hanging wire (FIG. 43A), rotarod (FIG. 43B) andescaping activity (FIG. 43C) tests, were performed every month toexamine effect of exosomal formulation on motor activity in PD mice. *p<0.05; ** p<0.005 compared to Parkin non-treated mice.

FIG. 44 shows the effect of Pluronic® P85 (P85) treatment on the numberof exosomes released by IC21 macrophages. The cells were incubated with1% Pluronic® P85, or Pluronic®-free media as a control for 4 hours,washed, and supplemented with serum-free media for another 20 hours.Following the incubation, exosomes were isolated from concomitant mediaand accounted by NTA. The treatment with Pluronic® increased productionof exosomes more than an order of magnitude. ** p<0.005.

FIG. 45 shows efficient transfection of IC21 cells by exosomes releasedfrom Raw264.7 macrophages pre-transfected with luciferase-encoding pDNA.Raw264.7 macrophages were treated with GP3K and mRNA, or GP3K and pDNA.Control cells were treated with GP3K only, or media. Following thetransfection, the cells were supplemented with 0.5% Pluronic® P85 (P85)solution for 18 hours at 37° C., or media as a control. Then, exosomeswere isolated from each macrophage treatment group and added to IC21macrophages for another 18 hours. Following the incubation, cells werelysed and accounted for luciferase. Only exosomes released from Raw264.7 macrophages pre-transfected with pDNA were able to transfect IC21macrophages. ** p<0.0005.

FIG. 46 shows characterization of exosomes isolated from humanpluripotent stem cells (hiPSC) by NTA. Exosomes released from hiPSC werecollected over 24 hours from concomitant media and washed with PBS. NTAshows particle size distribution with a major fraction at about 100 nm.

FIG. 47 shows characterization of exosomes isolated from humanpluripotent stem cells (hiPSC) by western blot. Exosomes released fromhiPSC were collected over 24 hours from concomitant media and washedwith PBS. Western blot shows significant amount of exosome-associatedprotein flotilin (lane 1), as well as LFA-1 (lane 2) in the isolatedexosomes. Protein ladder is shown for comparison (lane L).

FIGS. 48A-48D show delivery in vivo of exosomes released by hiPSC tocancer cells in a mouse model of pulmonary metastases. Exosomes releasedfrom hiPSC were collected over 24 hours from concomitant media andlabeled with hydrophobic fluorescent dye DID. Fluorescently-labeledexosomes were administered i.n. to C57BL/6 mice with metastases producedby intravenous 8FlmC-FLuc-3LL-M27 LLC cells. Four hours afteradministration of the exosomes the animals were sacrificed, the lungsextracted and sectioned and analyzed by confocal microscopy. Themicroscopy reveals (FIG. 48A) cancer cells, (FIG. 48B) DID-labeledexosomes, (FIG. 48C) nuclei labeled with DAPI, and (FIG. 48D)colocalization of the exosomes and cancer cells. The bar: 50 μm.

FIGS. 49A-49C show characterization exosomal formulations exoPTX andAA-PEG-exoPTX. PTX and vector moiety AA-PEG-DSPE was incorporated inexosomes by sonication procedure. (FIG. 49A) Loading Capacity (LC) forPTX in vectorized exosomes was measured by HPLC. Increasing amounts ofvector moiety resulted in LC decrease. The highest concentration ofAA-PEG-DSPE that did not lower the LC for PTX in exosomes was chosen forsubsequent experiment (shown by arrow). (FIG. 49B) Western blot dataindicated that formulations retained the exosome markers TSG101,flotillin, and LFA-1, a specific marker for lymphocytes. (FIG. 49C)Particle size was measured by NTA and DLS, the zeta potential wasmeasured by DLS.

FIG. 50 shows the effect of AA-PEG-DSPE incorporation and PTX loading onfluidity of exosomal membranes. Exosomes were labeled with BODIPY-PC,and examined by fluorescence polarization measurements. The ultrasoundtreatment significantly decreased microviscosity of exosomal membranescompared to naïve exosomes. The microviscosity of sonicated exosomes wasincreased with PTX loading and then further increased with incorporationof the lipid upon sonication. Values are means±SEM (n=4). Symbolsindicate the relative level of significance compared with naïve exosomes(p<0.05).

FIGS. 51A-51B shows accumulation of AA-vectorized exosomes in targetcancer cells. (FIG. 51A) 3LL-M27 cells were incubated withfluorescently-labeled AA-PEG-exo, or PEG-exo, or exo for various times,and accumulation levels were recorded. AA-PEG-exo were more readilytaken up by 3LL-M27 as compared to exo and PEG-exo. (FIG. 51B)AA-PEG-exo formulation showed a dose-dependent response to competitiveinhibition by AA, indicating that this formulation was targeted to thesigma receptor and enters cells by receptor mediated endocytosis.Results are expressed as number of exosomes/μg protein vs. concentrationof AA.

FIG. 52 shows importance of surface proteins on exosome accumulation in3LL-M27 cancer cells. Naïve (circle), sonicated (triangle), andAA-vectorized (cross) exosomes were incubated with proteinase K to stripsurface proteins, labeled with fluorescent dye (DIL), and accumulationof Proteinase K-treated exosomes (dashed line) or control exosomes(solid line) was examined in target cancer cells. Stripping the exosomalsurface proteins resulted in significant decreases in accumulationlevels in target cells for all formulations.

FIGS. 53A-53C show intracellular trafficking of AA-vectorized exosomesin cancer cells. Fluorescently labeled (DiL) exosomes were incubatedwith 3LL-M27 cells for one hour. Afterwards, cells were washed andstained with ER Tracker (FIG. 53A) or LysoTracker (FIG. 53B), orMitotracker (FIG. 53C). Areas of co-localization were evident in theimages. The bar: 20 μm.

FIGS. 54A-54I show co-localization of intravenously-deliveredAA-vectorized exosomes with pulmonary metastases. Exosomes were isolatedfrom macrophages conditioned media, and labelled with DiL dye (FIG. 54A,FIG. 54D). C57BL/6 mice were i.v. injected with 3LL-M27 cells transducedwith lentiviral vectors encoding the optical reporter GFP fluorescentprotein (FIG. 54B, FIG. 54 E). 7 days later, the mice with establishedpulmonary metastases (green) were i.v. injected with DiL-labelednon-vectorized exosomes (FIG. 54A), or AA-vectorized exosomes (FIG.54D). 4 hours later, mice were euthanized, perfused, lungs weresectioned, and stained with DAPI. The confocal images revealed asignificant co-localization of vectorized exosomes with metastases(94.4+0.8%), that was greater than those of non-vectorized exosomes(21.8+0.2%) (FIG. 54F). No exosomes were found in lungs of healthyanimals without metastases (FIGS. 54G-54I). The bar: 20 μm.

FIGS. 55A-55B show AA-PEG-ExoPTX induced potent anticancer effectagainst lung metastases in LLC mouse model. (FIG. 55A) C57BL/6 mice withestablished Luc/mCherry-3LL-M27 lung metastases were i.v. treated withi) saline, or ii) Taxol, or iii) exoPTX, or iv) AA-PEG-exoPTX. 18 dayslater, mice were sacrificed, perfused, and lungs slides were examined byconfocal microscopy. AA-PEG-exoPTX treatment resulted in a potentinhibition of metastases that was more effective than treatment withTaxol or exoPTX. The bar: 50 μm. (FIG. 55B) A survival curve of C57BL/6mice with established metastases was recorded for four treatmentgroups: 1) saline (diamonds), or 2) Taxol (squares), or 3) exoPTX(triangles), or 4) AA-PEG-exoPTX (crosses). A superior effect on micesurvival was recorded in AA-PEG-exoPTX treatment group (n=6).

DETAILED DESCRIPTION OF THE INVENTION

The present invention is explained in greater detail below. Thisdescription is not intended to be a detailed catalog of all thedifferent ways in which the invention may be implemented, or all thefeatures that may be added to the instant invention. For example,features illustrated with respect to one embodiment may be incorporatedinto other embodiments, and features illustrated with respect to aparticular embodiment may be deleted from that embodiment. In addition,numerous variations and additions to the various embodiments suggestedherein will be apparent to those skilled in the art in light of theinstant disclosure which do not depart from the instant invention.Hence, the following specification is intended to illustrate someparticular embodiments of the invention, and not to exhaustively specifyall permutations, combinations and variations thereof.

Unless the context indicates otherwise, it is specifically intended thatthe various features of the invention described herein can be used inany combination. Moreover, the present invention also contemplates thatin some embodiments of the invention, any feature or combination offeatures set forth herein can be excluded or omitted. To illustrate, ifthe specification states that a complex comprises components A, B and C,it is specifically intended that any of A, B or C, or a combinationthereof, can be omitted and disclaimed singularly or in any combination.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. The terminology used in thedescription of the invention herein is for the purpose of describingparticular embodiments only and is not intended to be limiting of theinvention.

Except as otherwise indicated, standard methods known to those skilledin the art may be used for production of recombinant and syntheticpolypeptides, antibodies or antigen-binding fragments thereof,manipulation of nucleic acid sequences, and production of transformedcells. Such techniques are known to those skilled in the art. See, e.g.,SAMBROOK et al., MOLECULAR CLONING: A LABORATORY MANUAL 2nd Ed. (ColdSpring Harbor, N.Y., 1989); F. M. AUSUBEL et al. CURRENT PROTOCOLS INMOLECULAR BIOLOGY (Green Publishing Associates, Inc. and John Wiley &Sons, Inc., New York).

All publications, patent applications, patents, nucleotide sequences,amino acid sequences and other references mentioned herein areincorporated by reference in their entirety.

As used in the description of the invention and the appended claims, thesingular forms “a,” “an” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise.

As used herein, “and/or” refers to and encompasses any and all possiblecombinations of one or more of the associated listed items, as well asthe lack of combinations when interpreted in the alternative (“or”).

Moreover, the present invention also contemplates that in someembodiments of the invention, any feature or combination of features setforth herein can be excluded or omitted.

Furthermore, the term “about,” as used herein when referring to ameasurable value such as an amount of a compound or agent of thisinvention, dose, time, temperature, and the like, is meant to encompassvariations of ±20%, ±10%, ±5%, ±1%, ±0.5%, or even±0.1% of the specifiedamount.

Unless otherwise indicated, all numbers expressing quantities ofingredients, properties such as reaction conditions, and so forth usedin the specification and claims are to be understood as being modifiedin all instances by the term “about”. Accordingly, unless indicated tothe contrary, the numerical parameters set forth in this specificationand claims are approximations that can vary depending upon the desiredproperties sought to be obtained by the presently-disclosed subjectmatter.

As used herein, ranges can be expressed as from “about” one particularvalue, and/or to “about” another particular value. It is also understoodthat there are a number of values disclosed herein, and that each valueis also herein disclosed as “about” that particular value in addition tothe value itself. For example, if the value “10” is disclosed, then“about 10” is also disclosed. It is also understood that each unitbetween two particular units is also disclosed. For example, if 10 and15 are disclosed, then 11, 12, 13, and 14 are also disclosed.

The transitional phrase “consisting essentially of” means that the scopeof a claim is to be interpreted to encompass the specified materials orsteps recited in the claim, “and those that do not materially affect thebasic and novel characteristic(s)” of the claimed invention. See, In reHerz, 537 F.2d 549, 551-52, 190 USPQ 461, 463 (CCPA 1976) (emphasis inthe original).

As used herein, the term “polypeptide” encompasses both peptides andproteins, unless indicated otherwise. The term also includespost-expression modifications of the polypeptide, for example,glycosylations, acetylations, phosphorylations and the like. Inaddition, protein fragments, analogs, mutated or variant proteins,fusion proteins and the like are included within the meaning ofpolypeptide.

A “polynucleotide,” “nucleic acid,” or “nucleotide sequence” is asequence of nucleotide bases, and may be RNA, DNA or DNA-RNA hybridsequences (including both naturally occurring and non-naturallyoccurring nucleotide), but is preferably either single or doublestranded DNA sequences.

By the terms “treat,” “treating,” or “treatment of” (or grammaticallyequivalent terms) it is meant that the severity of the subject'scondition is reduced or at least partially improved or amelioratedand/or that some alleviation, mitigation or decrease in at least oneclinical symptom is achieved and/or there is a delay in the progressionof the condition.

As used herein, the terms “prevent,” “prevents,” or “prevention” and“inhibit,” “inhibits,” or “inhibition” (and grammatical equivalentsthereof) are not meant to imply complete abolition of disease andencompasses any type of prophylactic treatment that reduces theincidence of the condition, delays the onset of the condition, and/orreduces the symptoms associated with the condition after onset.

An “effective,” “prophylactically effective,” or “therapeuticallyeffective” amount as used herein is an amount that is sufficient toprovide some improvement or benefit to the subject. Alternativelystated, an “effective,” “prophylactically effective,” or“therapeutically effective” amount is an amount that will provide somedelay, alleviation, mitigation, or decrease in at least one clinicalsymptom in the subject. Those skilled in the art will appreciate thatthe effects need not be complete or curative, as long as some benefit isprovided to the subject.

The term “isolated” may refer to protein, nucleic acid, compound, orcell that has been sufficiently separated from the environment withwhich it would naturally be associated, so as to exist in “substantiallypure” form. “Isolated” does not necessarily mean the exclusion ofartificial or synthetic mixtures with other compounds or materials, orthe presence of impurities that do not interfere with the fundamentalactivity, and that may be present, for example, due to incompletepurification.

The term “biological agent,” as used herein, refers to any compound ormolecule that exerts a biological effect when delivered to a cell or asubject. This includes therapeutic, prophylactic, neutral, or toxiceffects as well as detectable effects (e.g., a reporter molecule).

The term “small molecule,” as used herein, refers to a compound ormolecule having a molecular weight of less than about 1000 daltons.

The term “polymer” or “polymer chain” or “polymeric chain,” as usedherein interchangeably, refers to a molecule formed by covalent linkingof monomeric units.

The term “block copolymer,” as used herein, refers to a combination oftwo or more polymeric chains of constitutionally or configurationallydifferent features linked in a linear fashion. Such distinct polymericchains of block copolymers are termed “blocks.”

The term “amphiphilic block copolymer,” as used herein, refers to ablock copolymer comprised of at least one hydrophilic polymeric chainand at least one hydrophobic polymeric chain. Examples of hydrophilicpolymeric chains include polyethers (e.g., poly(ethylene oxide) (PEO)(or poly(oxyethylene) that is used interchangeably with poly(ethyleneglycol) (PEG)), polysaccharides (e.g., dextran), polyglycerol,homopolymers and copolymers of vinyl monomers (e.g., polyacrylamide,polyacrylic esters (e.g., polyacryloyl morpholine), polymethacrylamide,poly(N-(2-hydroxypropyl)methacrylamide, polyvinyl alcohol, polyvinylpyrrolidone, polyvinyltriazole, N-oxide of polyvinylpyridine, copolymerof vinylpyridine and vinylpyridine N-oxide) polyortho esters,polyaminoacids, polyglycerols, poly(2-oxazolines) (e.g.,poly(2-methyl-2-oxazoline), poly(2-ethyl-2-oxazoline) and copolymers),polysarcosine and derivatives thereof. Examples of hydrophobic polymericchains include poly(propylene oxide) (PPO) (or poly(oxypropylene) thatis used interchangeably with PPO), copolymers of poly(ethylene oxide)and PEO, polyalkylene oxide other than PEO and PPO, poly(2-oxazolines)(e.g., poly-(2-propyl-2-oxazoline), poly(2-butyl-2-oxazoline),2-isobutyl-oxazoline, 2-sec-butyl-2-oxazoline, 2-pentyl-2-oxazoline,2-heptyl-2-oxazoline, 2-benzyl-2-oxazoline, 2-nonyl-2-oxazoline, and thelike), polycaprolactone, poly(D,L-lactide), homopolymers and copolymersof hydrophobic aminoacids and derivatives of amino acids (e.g., alanine,valine, isoleucine, leucine, norleucine, phenylalanine, tyrosine,tryptophan, threonine, proline, cysteine, methionine, serine, glutamine,asparagine), poly(O-benzyl-L-aspartate) and the like.

The term “not naturally present in the exosome,” as used herein, refersto a biological agent that is not present in an exosome as it is foundin nature, e.g., exosomes as generated from a cell in a subject or inculture.

The term “functional polynucleotide,” as used herein, refers to apolynucleotide that has a biological function without being translatedinto a polypeptide. Examples include, without limitation, antisenseoligonucleotides, recombinant DNAs (rDNAs), plasmid DNAs (pDNAs),ribozymes, messenger RNAs (mRNAs), short (small) interfering RNAs(siRNAs), microRNAs, guide RNAs, and the like.

The term “cancer,” as used herein, refers to any benign or malignantabnormal growth of cells. Examples include, without limitation, breastcancer, prostate cancer, lymphoma, skin cancer, pancreatic cancer, coloncancer, melanoma, malignant melanoma, ovarian cancer, brain cancer,primary brain carcinoma, head-neck cancer, glioma, glioblastoma, livercancer, bladder cancer, non-small cell lung cancer, head or neckcarcinoma, breast carcinoma, ovarian carcinoma, lung carcinoma,small-cell lung carcinoma, Wilms' tumor, cervical carcinoma, testicularcarcinoma, bladder carcinoma, pancreatic carcinoma, stomach carcinoma,colon carcinoma, prostatic carcinoma, genitourinary carcinoma, thyroidcarcinoma, esophageal carcinoma, myeloma, multiple myeloma, adrenalcarcinoma, renal cell carcinoma, endometrial carcinoma, adrenal cortexcarcinoma, malignant pancreatic insulinoma, malignant carcinoidcarcinoma, choriocarcinoma, mycosis fungoides, malignant hypercalcemia,cervical hyperplasia, leukemia, acute lymphocytic leukemia, chroniclymphocytic leukemia, acute myelogenous leukemia, chronic myelogenousleukemia, chronic granulocytic leukemia, acute granulocytic leukemia,hairy cell leukemia, neuroblastoma, rhabdomyosarcoma, Kaposi's sarcoma,polycythemia vera, essential thrombocytosis, Hodgkin's disease,non-Hodgkin's lymphoma, soft-tissue sarcoma, osteogenic sarcoma, primarymacroglobulinemia, and retinoblastoma. In some embodiments, the canceris selected from the group of tumor-forming cancers.

The term “disorder associated with inflammation,” as used herein, refersto any disease, disorder, or condition in which inflammation is thecause and/or one of the symptoms.

The term “inflamed tissue,” as used herein, refers to a tissueexhibiting one or more signs of inflammation, such as immune cellactivation, vasodilation, edema, complement system activation, andleukocyte extravasation.

The present invention is based on the development of compositions usefulfor delivering biological agents, e.g., therapeutic or protective agentssuch as small molecules, polypeptides, and polynucleotides, to cells invitro and in vivo. The compositions provide improved delivery of agents,including crossing the BBB and targeting inflamed tissue, therebyimproving therapeutic effects while limiting immune response to theagents. The incorporation of biological agents into exosomes increasesthe circulation time, preserves therapeutic activity, and improvesdelivery to the central nervous system, cancer cells, the tumormicroenvironment, and inflamed tissue.

Thus, one aspect of the invention relates to a composition for deliveryof a biological agent to a cell, the composition comprising an exosomecomprising the biological agent, wherein the biological agent is notnaturally present in the exosome. The exosomes may be isolated frommammalian cells, for example, cancer cells, immune cells, such asmacrophages/monocytes or dendritic cells, or stem cells, such aspluripotent stem cells, and the like. The cells from which the exosomesare isolated may be selected for the characteristics desired in theexosomes, such as targeting specificity. For example, stem cells may bestimulated to particular development pathways such that exosomes derivedtherefrom will target specific tissues. Monocytes may be stimulated toproduce particular macrophages, e.g., M1 or M2 macrophages, prior toisolating exosomes.

Exosomes may be isolated from cells by methods known in the art and asdescribed herein. In some embodiments, the cells are cultured celllines, e.g., a macrophage cell line such as Raw 264.7. In otherembodiments, the cells are primary cells. In some embodiments, the cellsare isolated from a subject and cultured to produce exosomes. Inparticular embodiments, the cells are isolated from the same subject towhich the exosomes are to be delivered, e.g., autologous and/orallogeneic cells.

In some embodiments of the instant invention, the cells are treated by ablock copolymer or combination of several block copolymers, such asamphiphilic block copolymers, to increase the production of exosomes. Ina particular embodiment, the amphiphilic block copolymers comprise atleast one block of PEO and at least one block of PPO. In a particularembodiment, the amphiphilic block copolymer is a triblock ofPEO-PPO-PEO. Polymers comprising at least one block of PEO and at leastone block of PPO are commercially available under such generic tradenames as “lipoloxamers”, “Pluronic®,” “poloxamers,” and “synperonics.”Examples of poloxamers include, without limitation, Pluronic® L31, L35,F38, L42, L43, L44, L61, L62, L63, L64, P65, F68, L72, P75, F77, L81,P84, P85, F87, F88, L92, F98, L101, P103, P104, P105, F108, L121, L122,L123, F127, 10R5, 10R8, 12R3, 17R1, 17R2, 17R4, 17R8, 22R4, 25R1, 25R2,25R4, 25R5, 25R8, 31R1, 31R2, and 31R4. Pluronic® block copolymers aredesignated by a letter prefix followed by a two or a three digit number.The letter prefixes (L, P, or F) refer to the physical form of eachpolymer, (liquid, paste, or flakeable solid). The numeric code definesthe structural parameters of the block copolymer. The last digit of thiscode approximates the total weight content of PEO blocks in tens ofweight percent (for example, 80% weight if the digit is 8, or 10% weightif the digit is 1). The remaining first one or two digits encode themolecular mass of the central PPO block. To decipher the code, oneshould multiply the corresponding number by 300 to obtain theapproximate molecular mass in daltons (Da). Therefore Pluronic®nomenclature provides a convenient approach to estimate thecharacteristics of the block copolymer in the absence of referenceliterature. For example, the code ‘F127’ defines the block copolymer,which is a solid, has a PO block of approximately 3600 Da (12×300) and70% weight of EO. The precise molecular characteristics of eachPluronic® block copolymer can be obtained from the manufacturer.Amphiphilic block copolymers such as Pluronic® block copolymers may becharacterized by different hydrophilic-lipophilic balance (HLB) (Kozlovet al. (2000) Macromolecules, 33:3305-3313). The HLB value, whichtypically falls in the range of 1 to 31 for Pluronic® block copolymers,reflects the balance of the size and strength of the hydrophilic groupsand lipophilic groups of the polymer (see, for example, Attwood andFlorence (1983) “Surfactant Systems: Their Chemistry, Pharmacy andBiology,” Chapman and Hall, New York) and can be determinedexperimentally by, for example, the phenol titration method of Marszall(see, for example, “Parfumerie, Kosmetik”, Vol. 60, 1979, pp. 444-448;Rompp, Chemistry Lexicon, 8th Edition 1983, p. 1750; U.S. Pat. No.4,795,643). HLB values for Pluronic® polymers are available from BASFCorp. HLB values can be approximated by the formula: HLB=−36 y/x+y+33,wherein y is the number of hydrophobic propylene oxide units and x isthe number of hydrophilic ethylene oxide units, though HLB valuesprovided by BASF are preferred. Notably, as hydrophobicity increases,HLB decreases. In a particular embodiment, the amphiphilic blockcopolymer of the instant invention has an intermediate HLB or low HLB.For example, the HLB for the amphiphilic block copolymer useful on thisinvention may be about 20 or less, particularly about 18 or less,particularly about 16 or less. In some embodiments the HLB for theamphiphilic block copolymer is in the range from 12 to 18. In someembodiments, the molecular mass of the PPO block is between about 300and about 4000, e.g., between about 800 and about 3600, e.g., betweenabout 1000 and about 2900, e.g., between about 1400 and about 2500. Thephysical and molecular characteristics of Pluronic® polymers are wellknown in the art and can be found, for example, in Paschalis et al.,Colloids and Surfaces A: Physicochemical and Engineering Aspects 96,1-46 (1995) and Kozlov et al., Macromolecules 33:3305-3313 (2000),incorporated herein by reference. In some embodiments of the instantinvention, when block copolymers are used to increase production of theexosomes the block copolymers are added to the donor cells prior to orsimultaneously with the isolation of exosomes. In some embodiments, theconcentration of block copolymers added to donor cells is in the rangefrom about 0.01% to about 5%, e.g., between about 0.1% and about 1%. Insome embodiments, the donor cells are exposed to the block copolymersfor the period of from about 1 h to about 40 h before the exosomes areisolated, e.g., between about 4 and about 20 h before the exosomes areisolated.

The biological agent may be any agent that is desirable to deliver to acell and/or a subject. The agent may be a therapeutic agent, aprophylactic agent, a marker, a reporter, a research reagent, etc. Insome embodiments, the biological agent is a small molecule, e.g.,compounds such as synthetic and natural drugs. In other embodiments, thebiological agent is a macromolecule, e.g., a polypeptide,polynucleotide, polysaccharide, etc.

In some embodiments of the instant invention, the polypeptide is atherapeutic polypeptide, e.g., it effects amelioration and/or cure of adisease, disorder, pathology, and/or the symptoms associated therewith.The polypeptides may have therapeutic value against neurologicaldisorders (particularly of the CNS) including, without limitation,neurological degenerative disorders and neurodevelopmental disorders,such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington'sdisease (HD), Rett syndrome, stroke, trauma, infections, meningitis,encephalitis, gliomas, cancers (including brain metastasis), HIV-1associated dementia (HAD), HIV associated neurocognitive disorders(HAND), paralysis, amyotrophic lateral sclerosis (ALS or Lou Gehrig'sdisease), multiple sclerosis (MS), CNS-associated cardiovasculardisease, prion disease, obesity, metabolic disorders, inflammatorydisease, and lysosomal storage diseases (LSDs; such as, withoutlimitation, Gaucher's disease, Pompe disease, Niemann-Pick, Huntersyndrome (MPS II), Mucopolysaccharidosis I (MPS I), GM2-gangliosidoses,Gaucher disease, Sanfilippo syndrome (MPS IIIA), Tay-Sachs disease,Sandhoff's disease, Krabbe's disease, metachromatic leukodystrophy, andFabry disease). Therapeutically active polypeptides include, but are notlimited to, enzymes, antibodies, hormones, growth factors, otherpolypeptides, which administration to the brain can effect ameliorationand/or cure of a disease, disorder, pathology, and/or the symptomsassociated therewith. Neuroactive polypeptides useful in this inventioninclude but are not limited to endocrine factors, growth factors,hypothalamic releasing factors, neurotrophic factors, paracrine factors,neurotransmitter polypeptides, antibodies and antibody fragments whichbind to any of the above polypeptides (such neurotrophic factors, growthfactors, and others), antibodies and antibody fragments which bind tothe receptors of these polypeptides (such as neurotrophic factorreceptors), cytokines, endorphins, polypeptide antagonists, agonists fora receptor expressed by a CNS cell, polypeptides involved in lysosomalstorage diseases, and the like. In a particular embodiment, thetherapeutic protein exerts its effect on the CNS. In another particularembodiment, the therapeutic protein does not cross the BBB by itself.

In certain embodiments, the polypeptide is a neurotrophin, e.g.,selected from, without limitation, brain derived neurotrophic factor,nerve growth factor, neurotrophin 3, neurotrophin 4, glial cell derivedneurotrophic factor, artemin, neurturin, persephin, ciliary neurotrophicfactor, and any combination thereof.

Examples of other polypeptides include, without limitation, enzymes,such as catalase, telomerase, superoxide dismutase (SOD), glutathioneperoxidase, glutaminase, cytokines, endorphins (e.g., enkephalin),growth factors (e.g., epidermal growth factor (EGF), acidic and basicfibroblast growth factor (aFGF and bFGF), insulin-like growth factor I(IGF-I), brain-derived neurotrophic factor (BDNF), glial-derivedneurotrophic factor (GDNF), platelet derived growth factor (PDGF),vascular growth factor (VGF), nerve growth factor (NGF), insulin-likegrowth factor-II (IGF-II), tumor necrosis factor-B (TGF-B), leukemiainhibitory factor (LIF), various interleukins, and the like),antiapoptotic proteins (BCL-2, PI3 kinase, and the like), amyloid betabinders (e.g., antibodies), modulators of α-, β-, and/or γ-secretases,vasoactive intestinal peptide, leptin, acid alpha-glucosidase (GAA),acid sphingomyelinase, iduronate-2-sultatase (I2S), α-L-iduronidase(IDU), β-Hexosaminidase A (HexA), Acid β-glucocerebrosidase,N-acetylgalactosamine-4-sulfatase, α-galactosidase A, andneurotransmitters.

In certain embodiments, the biological agent is a polynucleotideencoding a polypeptide or a functional polynucleotide, e.g., a siRNA,microRNA, antisense oligonucleotide, etc.

In certain embodiments, the biological agent is an anticancer agent.Anticancer agents include, without limitation, 1) vinca alkaloids (e.g.,vinblastine, vincristine); 2) epipodophyllotoxins (e.g., etoposide andteniposide); 3) antibiotics (e.g., dactinomycin (actinomycin D),daunorubicin (daunomycin; rubidomycin), doxorubicin, bleomycin,plicamycin (mithramycin), and mitomycin (mitomycin C)); 4) enzymes(e.g., L-asparaginase); 5) biological response modifiers (e.g.,interferon-alfa); 6) platinum coordinating complexes (e.g., cisplatinand carboplatin); 7) anthracenediones (e.g., mitoxantrone); 8)substituted ureas (e.g., hydroxyurea); 9) methylhydrazine derivatives(e.g., procarbazine (N-methylhydrazine; MIH)); 10) adrenocorticalsuppressants (e.g., mitotane (o,p′-DDD) and aminoglutethimide); 11)adrenocorticosteroids (e.g., prednisone); 12) progestins (e.g.,hydroxyprogesterone caproate, medroxyprogesterone acetate, and megestrolacetate); 13) estrogens (e.g., diethylstilbestrol and ethinylestradiol); 14) antiestrogens (e.g., tamoxifen); 15) androgens (e.g.,testosterone propionate and fluoxymesterone); 16) antiandrogens (e.g.,flutamide): and 17) gonadotropin-releasing hormone analogs (e.g.,leuprolide). In another embodiment, the anticancer agents areanti-angiogenesis agents, such as antibodies to VEGF (e.g., bevacizumab(AVASTIN), ranibizumab (LUCENTIS)) and other promoters of angiogenesis(e.g., bFGF, angiopoietin-1), antibodies to alpha-v/beta-3 vascularintegrin (e.g., VITAXIN), angiostatin, endostatin, dalteparin, ABT-510,CNGRC peptide TNF alpha conjugate, cyclophosphamide, combretastatin A4phosphate, dimethylxanthenone acetic acid, docetaxel, lenalidomide,enzastaurin, paclitaxel, paclitaxel albumin-stabilized nanoparticleformulation (Abraxane), soy isoflavone (Genistein), tamoxifen citrate,thalidomide, ADH-1 (EXHERIN), AG-013736, AMG-706, AZD2171, sorafenibtosylate, BMS-582664, CHIR-265, pazopanib, PI-88, vatalanib, everolimus,suramin, sunitinib malate, XL184, ZD6474, ATN-161, cilenigtide, andcelecoxib.

In some embodiments, the exosome further comprises a targeting agent,e.g., an agent that targets the exosome to specific cells or tissues.Examples of targeting agents include, without limitation, receptors,ligands, antibodies, cell surface binding proteins, and substratebinding proteins. Targeting agents may be expressed in cells from whichthe exosomes are isolated such that the targeting agents are present inthe exosomes. Targeting agents may be attached to exosomes (e.g.,covalently or non-covalently) after the exosomes are isolated. In someembodiments, the targeting agents are attached to the exosomes through awater soluble polymer linker, for example, PEO (or PEG),poly(2-methyl-2-oxazoline) or poly(2-ethyl-2-oxazoline), polysarcosine,and derivatives thereof. These targeting groups can be attached to thesurface of exosomes using such polymeric linker that can be connected toa lipid group.

Work described in the examples below demonstrated that exosomes utilizedmultiple pathways to enter the cells, including clathrin-mediatedendocytosis, caveolae-mediated endocytosis and macropinocytosis. It wasadditionally shown that the integrin lymphocyte function associatedantigen-1 (LFA-1) present on exosomes plays a role in the uptake ofexosomes by cells. These pathways can be used advantageously to increasethe uptake of exosomes by cells as well as target the exosomes tospecific cells or tissues.

The methods of the current invention involve the use of exosomescontaining one or several useful biological agents, or use of severalexosomes containing different biological agents that can be administeredalone or with cells, simultaneously or separately from each other. Theexosomes may be in the same composition or may be in separatecompositions.

One aspect of the invention relates to methods of loading biologicalagents into exosomes. The biological agent can be loaded into theisolated exosome by methods known in the art and as described herein. Insome embodiments, the invention relates to a method of loading abiological agent into an exosome, comprising a step selected from thegroup consisting of:

a) incubating the biological agent with the exosome, optionally in thepresence of a saponin;

b) combining the biological agent and the exosome and subjecting them toa freeze-thaw cycle;

c) combining the biological agent and the exosome and subjecting them tosonication;

d) combining the biological agent and the exosome and subjecting them toextrusion; and

e) modifying exosomes with a molecule containing multiple charges andoptionally purifying the exosomes before adding the biological agent.The optimal loading method will depend at least in part on thecharacteristics of the biological agent, e.g., the size, charge,hydrophobicity, etc.

In some embodiments, method a) comprises incubating the biological agentwith the exosome, e.g., at a temperature of about 20° C. to about 40°C., e.g., at about room temperature, e.g., for at least about 4 h, e.g.,at least about 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, or 24 h or any rangetherein. In some embodiments, agents such as saponins may be added tothe mixture, with or without shaking, e.g., at a concentration of about0.05% to 1%, e.g., about 0.2%, e.g., for about 5 minutes to about 60minutes e.g., for about 20 minutes.

In some embodiments, method b) comprises combining the biological agentand the exosome and subjecting them to a freeze at about −80° C. and athaw at about room temperature, which may be repeated 1 or more times,e.g., 1, 2, 3, 4, or 5 or more times.

In some embodiments, method c) comprises sonicating the mixture for 1 ormore pulses, e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 pulses or more,followed by cooling down on ice and optionally applying further pulses.The pulses may be for about 4 seconds with about a 2 second pausein-between pulses.

In some embodiments, method d) comprises extruding the mixture throughan extruder 1 or more times, e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10times or more. The pore diameter of the extruder may be about 50 nm toabout 1000 nm, e.g., about 100 nm to about 400 nm, e.g., about 200 nm.

In some embodiments, the exosomes are modified with molecules containingmultiple charges to increase incorporation of a biological agent intoexosomes, and/or stability of the exosomes with the biological agent. Incertain embodiments, exosomes may be modified with a polyion or a lipidthat can contain multiple charges that can be either positive ornegative charges. It is preferred that such polyion or lipid moleculecontain at least three charged groups, preferably at least five chargedgroups, more preferably at least seven charged groups, still morepreferably at least nine charged groups. In one preferred embodiment,the exosomes are modified with multivalent cationic molecules. Examplesinclude polycations that can be optionally modified with one or severallipid moieties. Preferred polycations include polyamines (e.g.,spermine, polyspermine, polyethyleneimine, polypropyleneimine,polybutileneimine, polypentyleneimine, polyhexyleneimine and copolymersthereof), copolymers of tertiary amines and secondary amines, partiallyor completely quaternized amines, the quaternary ammonium salts of thepolycation fragments, polypeptides such as poly-L-lysine, poly-D-lysine,poly-L-arginine, poly-D-arginine and their copolymers, N-substitutedpolyaspartamides such as poly[N-(2-aminoethyl)aspartamide] [PAsp(EDA)],poly{N—[N′-(2-aminoethyl)-2-aminoethyl]aspartamide [PAsp(DET)],poly(N—{N′—[N″-(2-aminoethyl)-2-aminoethyl]-2-aminoethyl)aspartamide)[PAsp(TET)],poly-[N—(N′—{N″—[N′″-(2-aminoethyl)-2-aminoethyl]-2-aminoethyl)-2-aminoethyl)aspartamide][PAsp(TEP)], poly(amidoamine)s and the like. Particularly preferredpolycation fragments are those having a plurality of cationic repeatingunits of the formula —N—R⁰, wherein R⁰ is a straight chain aliphaticgroup of 2 to 6 carbon atoms, which may be substituted. Each —NHR⁰—repeating unit in a polycation can be the same or different from another—NHR⁰— repeating unit in the fragment. Examples of polyanions includebut are not limited to poly-L-glutamic acid, poly-D-glutamic acid,poly-L-aspartic acid, poly-D-aspartic acid and their copolymers, and thelike. The polycations and polyanions of the invention can be randomlybranched or have a dendrimer architecture. In some embodiments, thepolyion of this invention is covalently linked to a lipid moiety. Insome embodiments, the polyions can be covalently linked to lipidmoieties or covalently linked to exosomes using conjugation reagentsknown in the art (see e.g., Hermanson G. T., Bioconjugate Techniques 3dEd. (Academic Press, N Y, 2013). The lipid moieties can be natural orsynthetic hydrophobic molecules comprising long chain aliphatic groupsthat can be saturated or unsaturated or aromatic groups that can beincorporated into the hydrophobic tail of a lipid. The preferred lipidmoieties may be long chain alcohols and amines, fatty acids,glycerolipids, glycerophospholipids, sphingolipids, sterol lipids,prenol lipids, saccharolipids, polyketides and their derivatives.Examples of commercially available multivalent lipids includeN1-[2-((1S)-1-[(3-aminopropyl)amino]-4-[di(3-aminopropyl)amino]butylcarboxamido)-ethyl]-3,4-di[oleyloxy]-benzamide)(MVL5) available from Avanti Polar Lipids,dioctadecylamidoglycylspermine (DOGS) available as Promega™Transfectam™,2,3-dioleyloxy-N-[2-(sperminecarboxamido)ethyl]-N,N-dimethyl-1-propylammoniumchloride (DOSPA) available from GOBCO/BRL and the like. Examples ofmultivalent lipids with dendritic headgroup include MVLBG2 (Evert etal., J Am Chem Soc. 128(12):3998 (2006)). Without wishing to limit thisinvention to a specific theory it is believed that the lipid moietyincorporates into the membrane of the exosomes. The multivalent lipidhead groups partially interact with the negatively charged lipidspresent in the exosome membranes but due to presence multiple chargesretain cationic charges exposed for interaction with the biologicalagents of this invention. It is preferred that after incorporation ofthe polyion or a lipid molecule into the exosomes the exosomes arepurified from the unincorporated polyion or a lipid molecule. Themodified exosomes may be then loaded with a biological agent.

An additional aspect of the invention relates to a method of deliveringa biological agent to a cell, comprising contacting the cell with thecomposition of the invention, thereby delivering the biological agent tothe cell.

A further aspect of the invention relates to a method of enhancingdelivery of a biological agent to a cancer cell, comprising contactingthe cell with the composition of the invention, thereby delivering thebiological agent to the cell. The delivery of the biological agent isenhanced relative to the agent without an exosome.

A further aspect of the invention relates to a method of enhancingdelivery of a biological agent to a cell in a tumor microenvironment,comprising contacting the cell with the composition of the invention,thereby delivering the biological agent to the cell. The delivery of thebiological agent is enhanced relative to the agent without an exosome.The tumor microenvironment is the cellular environment in which thetumor exists, including surrounding blood vessels, immune cells,fibroblasts, bone marrow-derived inflammatory cells, lymphocytes,signaling molecules and the extracellular matrix.

Another aspect of the invention relates to a method of enhancingdelivery of a biological agent to a central nervous system cell,comprising contacting the cell with the composition of the invention,thereby delivering the biological agent to the cell. The delivery of thebiological agent is enhanced relative to the agent without an exosome.Central nervous system cells include, without limitation, neurons andglial cells, including astrocytes, oligodendrocytes, and microglia.

In some embodiments, the cell is an in vitro cell, e.g., a primary cellor cell line in culture. In other embodiments, the cell is in a subject,e.g., an animal model of a disorder or a subject in need of treatment.

An additional aspect of the invention relates to a method of deliveringa biological agent to a subject, comprising delivering the compositionof the invention to the subject, thereby delivering the biological agentto the subject.

A further aspect of the invention relates to a method of delivering abiological agent across the BBB of a subject, comprising delivering thecomposition of the invention to the subject, thereby delivering thebiological agent across the BBB of the subject.

Another aspect of the invention relates to a method of delivering abiological agent to inflamed tissue of a subject, comprising deliveringthe composition of the invention to the subject, thereby delivering thebiological agent to inflamed tissue of the subject. In some embodiments,the inflamed tissue is central nervous system tissue. In someembodiments, the inflamed tissue is a tumor microenvironment.

An additional aspect of the invention relates to a method of treating adisorder in a subject in need thereof, comprising delivering atherapeutically effective amount of a composition of the invention tothe subject, wherein the biological agent is effective for treating thedisorder, thereby treating the disorder in the subject.

In some embodiments, the disorder is associated with inflammation. Incertain embodiments, the disorder is cancer or a central nervous systemdisorder. In any of the methods of the invention, the composition may bedelivered by any route effective to deliver the exosomes to the targetcells and/or tissues, e.g., intranasally or intravenously. In any of themethods of the invention, the exosomes may be isolated from autologouscells of the subject and administered to the subject.

Another aspect of the invention relates to the use of the exosomes ofthe invention to deliver polynucleotides to cells. The compositions ofthe invention provide efficient transfection of polynucleotides intocells compared to transfection techniques known in the art. Thus, oneaspect of the invention relates to a method of transfecting a cell witha polynucleotide, comprising contacting the cell with compositioncomprising an exosome comprising the polynucleotide, wherein the exosomeis isolated from a macrophage or a monocyte, and wherein thepolynucleotide is not naturally present in the exosome. In someembodiments, the polynucleotide is a plasmid, DNA fragment, mRNA, siRNA,microRNA, tRNA, or rRNA.

The polynucleotide may be loaded into the exosome using methods known inthe art and as described herein. In some embodiments, the polynucleotideand the exosome are incubated together, optionally in the presence of apolycation, e.g., polyethyleneimine. In some embodiments, the exosomesare modified with molecules containing multiple positive charges such aspolycations, polycations modified with lipid molecules, and/ormultivalent cationic lipids before incorporation of a polynucleotideinto exosomes. It is preferred that polycation or lipid molecule containat least three positively charged groups, preferably at least fivecharged groups, more preferably at least seven charged groups, stillmore preferably at least nine charged groups. It is preferred that afterincorporation of the polycation or a lipid molecule into the exosomesthe exosomes are purified from the unincorporated polyion or a lipidmolecule. The modified exosomes may be then loaded with apolynucleotide.

In some embodiments, the cell is an in vitro cell, e.g., a primary cellor cell line in culture. In other embodiments, the cell is in a subject,e.g., an animal model of a disorder or a subject in need of treatment.In certain embodiments, the cell is a tumor cell or tumor cell line or acell in the tumor microenvironment. In certain embodiments, the cell isa central nervous system cell or central nervous system cell line.

In some embodiments, the exosomes may be isolated from autologousmacrophages or monocytes of the subject and administered to the subject.

In some embodiments, the invention relates to a method of loading abiological agent into an exosome, comprising:

a) loading a donor cell with a biological agent that optionally can beincorporated into a nanoparticle comprising a polymer or a lipid, suchas polymeric micelle or a polyion complex;

b) culturing the donor cells to allow for formation of exosomes; and

c) isolating exosomes loaded with the biological agent from these cells.

It is preferred that a biological agent is incorporated in ananoparticle and then these nanoparticles are added to the donor cells.The nanoparticles may have a diameter less than about 300 nm, preferablyless than about 150 nm, more preferably between about 5 nm and 100 nm,still more preferably between about 10 nm and about 60 nm. Thenanoparticles may be comprised of polymer and biological agent. Examplesof nanoparticles useful in this invention include but are not limited topolymeric micelles, polyion complexes, polyion complex micelles alsoknown as “block ionomer complexes”, nanogels, lipid nanoparticles,liposomes and the like (Kabanov and Vinogradov, Angew. Chem. Int. Ed.Engl. 48(30):5418-5429 (2009)). In some preferred embodiments biologicalagents are incorporated in polymeric micelles of block copolymers. Insome aspects of the invention hydrophobic and water-insoluble or poorlysoluble biological agents are incorporated into polymeric micellesformed by amphiphilic block copolymers. Unexpectedly, exposure of donorcells to polymeric micelles formed by amphiphilic block copolymersincreased entrapment of biological agents into exosomes. Withoutlimiting this invention to a specific theory it is believed thatwater-insoluble or poorly soluble small molecules are solubilized in thecore of the micelles formed by the hydrophobic blocks of the blockcopolymer and the drug-loaded micelles are stabilized in aqueous mediadue to formation of the shell by the hydrophilic blocks of the blockcopolymer. Various block copolymers are available in the art forpreparation of polymeric micelles (Kabanov and Alakhov, Crit. Rev. Ther.Drug Carrier Syst. 19 (1):1-73 (2002)). The amphiphilic block copolymerscomprising at least one block of PEO and at least one block of PPO arepreferred for incorporation of biological agents. In a particularembodiment, the amphiphilic block copolymer is a triblock ofPEO-PPO-PEO. In another embodiment the amphiphilic block copolymers ofpoly(2-oxazolines) comprising at least one hydrophilic poly(2-oxazoline)block (such as poly(2-methyl-2-oxazoline) or poly(2-ethyl-2-oxazoline)and at least one hydrophobic poly(2-oxazoline) block (such aspoly-(2-propyl-2-oxazoline), poly(2-butyl-2-oxazoline),2-isobutyl-oxazoline, 2-sec-butyl-2-oxazoline, 2-pentyl-2-oxazoline,2-heptyl-2-oxazoline, 2-benzyl-2-oxazoline, 2-nonyl-2-oxazoline, and thelike) are preferred for incorporation of biological agents. Polymericmicelles having high loading capacity of incorporating water-insolubleor poorly soluble small molecules are particularly preferred for thetreatment of donor cells. The loading capacity is defined herein as theweight percent of incorporated biological agent relative to the totalweight of the biological agent and block copolymer, and can becalculated using the formulaLC=M_(biological agent)/(M_(biological agent)+M_(block copolymer))×100%,where M_(biological agent) and M_(block copolymer) are the weightamounts of the solubilized biological agent and block copolymer in thesolution (He et al., Biomaterials 101:296-309 (2016)). It is preferredthat the LC is at least 5%, more preferred at least 10%, still morepreferred at least 15%. In some embodiments the biological agents areincorporated into polyion complexes. In such embodiments couplingbiological agents with polyelectrolytes may produce the polyioncomplexes (see Kabanov and Kabanov, Bioconjug. Chem. 6 (1):7-20 (1995)).In some preferred embodiments the block copolymers comprising at leastone water-soluble nonionic block and at least one polyion block areused. Particularly preferred nonionic blocks are PEO (or PEG),poly(2-methyl-2-oxazoline) or poly(2-ethyl-2-oxazoline), polysarcosineand derivatives thereof. Polypeptides and polynucleotides can beincorporated into polyion complexes with such block copolymers (see, forexample, Vinogradov et al., Bioconjug. Chem. 9 (6): 805-812 (1998);Batrakova, et al., Bioconjug. Chem. 18(5):1498-1506 (2007); Manickam etal., J. Control. Release 162(3):636-645 (2012)). Without wishing to bebound to a specific theory such polyion complexes also known in the artas “polyion complex micelles” or “block ionomer complexes” have acore-shell architecture with the polyion block neutralized biologicalagent complex forming the core and the nonionic block forming the shell.Upon exposure to cells these complexes may be taken up by the cells anddue to their dynamic nature these complexes can release incorporatedbiological agent inside the cells. Exposure of donor cells to suchcomplexes results in release of the polypeptides in the exosomes,however, the yield of such exosomes loaded with polypeptides is low(Haney et al., Nanomedicine (Lond) 6(7):1215-30 (2011)). Unexpectedly,treating the donor cells with polyion complexes combined with concurrentor subsequent treatment with amphiphilic block copolymers results in theincreased production of exosomes loaded with polypeptides. Since thetrafficking and distribution of the polynucleotides and proteins insidecells is vastly different it is unexpected that exposure of donor cellsto polyion complexes of polynucleotides results in loading of exosomeswith these polynucleotides. Unexpectedly, treating the donor cells withpolyion complexes combined with concurrent or subsequent treatment withamphiphilic block copolymers results in the increased production ofexosomes loaded with polynucleotides. The donor cells may be culturedwith nanoparticles carrying a biological agent for from about 1 hour toabout 96 hours. The cells may be optionally treated with a blockcopolymer to increase the yield (amount) of exosomes loaded with abiological agent. In a particular embodiment, the amphiphilic blockcopolymers comprise at least one block of PEO and at least one block ofPPO. In a particular embodiment, the amphiphilic block copolymer is atriblock of PEO-PPO-PEO. In these embodiments it is preferred that theconcentration of block copolymers added to donor cells is in the rangefrom about 0.01% to 5%, more preferred between 0.1% and 1%. It is alsopreferred that the donor cells are exposed to the block copolymers forthe period of from about 1 h to about 40 h before the exosomes areisolated, more preferred between about 4 and about 20 h before theexosomes are isolated.

In another aspect the invention relates to a method of loading abiological agent into an exosome, comprising:

-   -   a) transfecting a donor cell with a polynucleotide that        optionally can be incorporated into a nanoparticle comprising a        polymer or a lipid, such as a cationic polymer or a cationic        lipid;    -   b) culturing the cells to allow for formation of exosomes;    -   c) isolating exosomes from the cells.

The isolated exosomes may carry the DNA, RNA and/or protein produced asa result of the transfection of the cells with the polynucleotide. Thecells optionally may be treated with a block copolymer to increase theyield (amount) of exosomes loaded with a biological agent. In aparticular embodiment, the amphiphilic block copolymers comprise atleast one block of PEO and at least one block of PPO. In a particularembodiment, the amphiphilic block copolymer is a triblock ofPEO-PPO-PEO. In these embodiments it is preferred that the concentrationof block copolymers added to donor cells is in the range from about0.01% to about 5%, more preferred between about 0.1% and about 1%. It isalso preferred that the donor cells are exposed to the block copolymersfor the period of from about 1 h to about 40 h before the exosomes areisolated, more preferred between about 4 and about 20 h before theexosomes are isolated.

The present invention further provides a composition comprising theexosomes of the invention and a suitable carrier, e.g., apharmaceutically acceptable carrier.

By “pharmaceutically acceptable” it is meant a material that is notbiologically or otherwise undesirable, i.e., the material can beadministered to a subject without causing any undesirable biologicaleffects such as toxicity.

The compositions of the invention can optionally comprise medicinalagents, pharmaceutical agents, carriers, adjuvants, dispersing agents,diluents, and the like.

The exosomes of the invention can be formulated for administration in apharmaceutical carrier in accordance with known techniques. See, e.g.,Remington, The Science And Practice of Pharmacy (22^(nd) Ed. 2012). Inthe manufacture of a pharmaceutical formulation according to theinvention, the exosomes are typically admixed with, inter alia, anacceptable carrier. The carrier can be a solid or a liquid, or both, andis preferably formulated with the exosomes as a unit-dose formulation,for example, a tablet, which can contain from 0.01 or 0.5% to 95% or 99%by weight of the exosomes. One or more exosomes can be incorporated inthe formulations of the invention, which can be prepared by any of thewell-known techniques of pharmacy.

A further aspect of the invention is a method of treating subjects invivo, comprising administering to a subject a pharmaceutical compositioncomprising the exosomes of the invention in a pharmaceuticallyacceptable carrier, wherein the pharmaceutical composition isadministered in a therapeutically effective amount. Administration ofthe exosomes of the present invention to a human subject or an animal inneed thereof can be by any means known in the art for administeringcompounds.

Non-limiting examples of formulations of the invention include thosesuitable for oral, rectal, buccal (e.g., sub-lingual), vaginal,parenteral (e.g., subcutaneous, intramuscular including skeletal muscle,cardiac muscle, diaphragm muscle and smooth muscle, intradermal,intravenous, intraperitoneal), topical (i.e., both skin and mucosalsurfaces, including airway surfaces), intranasal, transdermal,intraarticular, intracranial, intrathecal, and inhalationadministration, administration to the liver by intraportal delivery, aswell as direct organ injection (e.g., into the liver, into a limb, intothe brain or spinal cord for delivery to the central nervous system,into the pancreas, or into a tumor or the tissue surrounding a tumor).The most suitable route in any given case will depend on the nature andseverity of the condition being treated and on the nature of theparticular compound which is being used. In some embodiments, it may bedesirable to deliver the formulation locally to avoid any side effectsassociated with systemic administration. For example, localadministration can be accomplished by direct injection at the desiredtreatment site, by introduction intravenously at a site near a desiredtreatment site (e.g., into a vessel that feeds a treatment site). Insome embodiments, the formulation can be delivered locally to ischemictissue. In certain embodiments, the formulation can be a slow releaseformulation, e.g., in the form of a slow release depot.

For injection, the carrier will typically be a liquid, such as sterilepyrogen-free water, pyrogen-free phosphate-buffered saline solution,bacteriostatic water, or Cremophor EL[R] (BASF, Parsippany, N.J.). Forother methods of administration, the carrier can be either solid orliquid.

Formulations of the present invention suitable for parenteraladministration comprise sterile aqueous and non-aqueous injectionsolutions of the compound, which preparations are preferably isotonicwith the blood of the intended recipient. These preparations can containanti-oxidants, buffers, bacteriostats and solutes which render theformulation isotonic with the blood of the intended recipient. Aqueousand non-aqueous sterile suspensions can include suspending agents andthickening agents. The formulations can be presented in unit/dose ormulti-dose containers, for example sealed ampoules and vials, and can bestored in a freeze-dried (lyophilized) condition requiring only theaddition of the sterile liquid carrier, for example, saline orwater-for-injection immediately prior to use.

Extemporaneous injection solutions and suspensions can be prepared fromsterile powders, granules and tablets of the kind previously described.For example, in one aspect of the present invention, there is providedan injectable, stable, sterile composition comprising exosomes of theinvention, in a unit dosage form in a sealed container. The exosomes areprovided in the form of a lyophilizate which is capable of beingreconstituted with a suitable pharmaceutically acceptable carrier toform a liquid composition suitable for injection thereof into a subject.The unit dosage form typically comprises from about 10 mg to about 10grams of the exosomes. When the compound or salt is substantiallywater-insoluble, a sufficient amount of emulsifying agent which ispharmaceutically acceptable can be employed in sufficient quantity toemulsify the exosomes in an aqueous carrier. One such useful emulsifyingagent is phosphatidyl choline.

The composition can alternatively be formulated for nasal administrationor otherwise administered to the lungs of a subject by any suitablemeans, e.g., administered by an aerosol suspension of respirableparticles comprising the exosomes, which the subject inhales. Therespirable particles can be liquid or solid. The term “aerosol” includesany gas-borne suspended phase, which is capable of being inhaled intothe bronchioles or nasal passages. Specifically, aerosol includes agas-borne suspension of droplets, as can be produced in a metered doseinhaler or nebulizer, or in a mist sprayer. Aerosol also includes a drypowder composition suspended in air or other carrier gas, which can bedelivered by insufflation from an inhaler device, for example. SeeGanderton & Jones, Drug Delivery to the Respiratory Tract, Ellis Horwood(1987); Gonda (1990) Critical Reviews in Therapeutic Drug CarrierSystems 6:273-313; and Raeburn et al., J. Pharmacol. Toxicol. Meth.27:143 (1992). Aerosols of liquid particles comprising the exosomes canbe produced by any suitable means, such as with a pressure-drivenaerosol nebulizer or an ultrasonic nebulizer, as is known to those ofskill in the art. See, e.g., U.S. Pat. No. 4,501,729. Aerosols of solidparticles comprising the exosomes can likewise be produced with anysolid particulate medicament aerosol generator, by techniques known inthe pharmaceutical art.

In some embodiments, the compositions are delivered byintranasal-to-brain (INB) delivery. INB delivery may be carried outusing techniques known in the art. In particular, the compositions ofthe invention may be delivered into the upper nasal turbinate area closeto the olfactory bulb (e.g., at the cribriform plate). Suitable carriersand formulations for intranasal delivery are known in the art and aredescribed above.

For oral administration, the exosomes can be administered in soliddosage forms, such as capsules, tablets, and powders, or in liquiddosage forms, such as elixirs, syrups, and suspensions. Exosomes can beencapsulated in gelatin capsules together with inactive ingredients andpowdered carriers, such as glucose, lactose, sucrose, mannitol, starch,cellulose or cellulose derivatives, magnesium stearate, stearic acid,sodium saccharin, talcum, magnesium carbonate and the like. Examples ofadditional inactive ingredients that can be added to provide desirablecolor, taste, stability, buffering capacity, dispersion or other knowndesirable features are red iron oxide, silica gel, sodium laurylsulfate, titanium dioxide, edible white ink and the like. Similardiluents can be used to make compressed tablets. Both tablets andcapsules can be manufactured as sustained release products to providefor continuous release of medication over a period of hours. Compressedtablets can be sugar coated or film coated to mask any unpleasant tasteand protect the tablet from the atmosphere, or enteric-coated forselective disintegration in the gastrointestinal tract. Liquid dosageforms for oral administration can contain coloring and flavoring toincrease patient acceptance.

Formulations suitable for buccal (sub-lingual) administration includelozenges comprising the compound in a flavored base, usually sucrose andacacia or tragacanth; and pastilles comprising the exosomes in an inertbase such as gelatin and glycerin or sucrose and acacia.

Formulations suitable for rectal administration are preferably presentedas unit dose suppositories. These can be prepared by admixing theexosomes with one or more conventional solid carriers, for example,cocoa butter, and then shaping the resulting mixture.

Formulations suitable for topical application to the skin preferablytake the form of an ointment, cream, lotion, paste, gel, spray, aerosol,or oil. Carriers which can be used include petroleum jelly, lanoline,polyethylene glycols, alcohols, transdermal enhancers, and combinationsof two or more thereof.

Formulations suitable for transdermal administration can be presented asdiscrete patches adapted to remain in intimate contact with theepidermis of the recipient for a prolonged period of time. Formulationssuitable for transdermal administration can also be delivered byiontophoresis (see, for example, Tyle, Pharm. Res. 3:318 (1986)) andtypically take the form of an optionally buffered aqueous solution ofthe compound. Suitable formulations comprise citrate or bis\tris buffer(pH 6) or ethanol/water and contain from 0.1 to 0.2M of the compound.

Alternatively, one can administer the exosomes in a local rather thansystemic manner, for example, in a depot or sustained-releaseformulation.

In the case of water-insoluble compositions, a pharmaceuticalcomposition can be prepared containing the water-insoluble compound,such as for example, in an aqueous base emulsion. In such an instance,the composition will contain a sufficient amount of pharmaceuticallyacceptable emulsifying agent to emulsify the desired amount of thecompound. Particularly useful emulsifying agents include phosphatidylcholines and lecithin.

In particular embodiments, the composition is administered to thesubject in a therapeutically effective amount, as that term is definedabove. Dosages of pharmaceutically active compounds can be determined bymethods known in the art, see, e.g., Remington's Pharmaceutical Sciences(Maack Publishing Co., Easton, Pa.). The therapeutically effectivedosage of any specific compound will vary somewhat from compound tocompound, and patient to patient, and will depend upon the condition ofthe patient and the route of delivery. As a general proposition, adosage from about 0.1 to about 50 mg/kg will have therapeutic efficacy,with all weights being calculated based upon the weight of the compound,including the cases where a salt is employed. Toxicity concerns at thehigher level can restrict intravenous dosages to a lower level such asup to about 10 mg/kg, with all weights being calculated based upon theweight of the compound, including the cases where a salt is employed. Adosage from about 10 mg/kg to about 50 mg/kg can be employed for oraladministration. Typically, a dosage from about 0.5 mg/kg to 5 mg/kg canbe employed for intramuscular injection. Particular dosages are about 1μmol/kg to 50 μmol/kg, and more particularly to about 22 μmol/kg and to33 μmol/kg of the compound for intravenous or oral administration,respectively.

In particular embodiments of the invention, more than one administration(e.g., two, three, four, or more administrations) can be employed over avariety of time intervals (e.g., hourly, daily, weekly, monthly, etc.)to achieve therapeutic effects.

The present invention finds use in veterinary and medical applications.Suitable subjects include both avians and mammals, with mammals beingpreferred. The term “avian” as used herein includes, but is not limitedto, chickens, ducks, geese, quail, turkeys, and pheasants. The term“mammal” as used herein includes, but is not limited to, humans,bovines, ovines, caprines, equines, felines, canines, lagomorphs, etc.Human subjects include neonates, infants, juveniles, and adults. Inother embodiments, the subject is an animal model of a disorder, e.g., aCNS disorder or cancer. In certain embodiments, the subject is in needof treatment for a disorder, i.e., a subject that has a disorder or isat increased risk for a disorder relative to the general population.

Having described the present invention, the same will be explained ingreater detail in the following examples, which are included herein forillustration purposes only, and which are not intended to be limiting tothe invention.

Example 1 Exosomes as Drug Delivery Vehicles for PD Therapy

In this example exosomes are loaded with a protein, catalase, and usedfor delivery of this protein to the site of inflammation in the brain totreat a neurodegenerative disease. The delivery of catalase to the brainusing exosomes as drug delivery vehicles, and therapeutic effect of thecatalase-loaded exosomes are demonstrated using an animal model of PD.

Methods

Reagents: Catalase from bovine liver was purchased from Calbiochem (SanDiego, Calif.). A lipophilic fluorescent dyes,1,1′-dioctadecyl-3,3,3′,3′-tetramethylindo-carbocyanine perchlorate(DIL), and2-(5-(1,3-dihydro-3,3-dimethyl-1-octadecyl-2H-indol-2-ylidene)-1,3-pentadienyl)-3,3-dimethyl-1-octadecyl-perchlorate(DID) were purchased from Invitrogen (Carlsbad, Calif., USA).6-hydroxydopamine (6-OHDA), lipopolysaccharides (LPS), rhodamineisothiocyanate (RITC), and Triton X-100 were obtained from Sigma-Aldrich(St. Louis, Mo., USA). Interferon gamma (INT-γ) was purchased fromPeprotech Inc. (RockyHill, N.J., USA).

Cells: A mouse macrophage cell line (Raw 264.7) was purchased fromAmerican Type Culture Collection (ATCC, Manassas, Va., USA, cat#TIB-71), and cultured in Dulbecco's Modified Eagle's Media (DMEM)(Invitrogen) supplemented with 10% (v/v) heat-inactivated fetal bovineserum (FBS). Neuronal PC12 rat adrenal pheochromocytoma cell line wasobtained from ATCC, and cultured in Dulbecco's modified Eagle medium(Hyclone, South Logan, Utah, USA) supplemented with 10% FBS, and 1%(v/v) of both penicillin and streptomycin. The cells were grown in anincubator with optimal culture conditions of 37° C. and 5% CO₂, and themedium was routinely replaced every 2-3 days.

Bone marrow derived macrophages (BMM) were obtained by differentiationof bone marrow stem cells extracted from murine femurs (C57BL/6, femalemice) as described in Dou et al. (Blood 108:2827 (2006)). The cells werecultured for 10 days in media supplemented with 1000 U/mL macrophagecolony-stimulating factor (MCSF). The purity of monocyte culture wasdetermined by flow cytometry using FACS Calibur (BD Biosciences, SanJose, Calif., USA). Mouse primary cultured cortical neurons anddopaminergic (DA) neurons from substantia nigra pars compacta (SNpc)were isolated from mouse pups cortex and midbrain as described (Pruszaket al., Curr. Protoc. Stem Cell Biol. Chapter 2, Unit 2D 5 (2009)).

Isolation of exosomes: Concomitant media from Raw 264.7 macrophagesgrown on 75T flasks (20×10⁶ cells/flask) was collected, and exosomeswere isolated using gradient centrifugation (Thery et al., Curr. Protoc.Cell Biol. Chapter 3, Unit 3 22 (2006)). In brief, the culturesupernatants were cleared of cell debris and large vesicles bysequential centrifugation at 300 g for 10 min, 1000 g for 20 min, and10,000 g for 30 min, followed by filtration using 0.2 μm syringefilters. Then, the cleared sample was spun at 100,000 g for one hour topellet the exosomes, and supernatant was collected. The collectedexosomes (10¹¹-10¹² exosomes/flask) were washed twice with phosphatebuffer solution (PBS). To avoid contamination by the FBS-derivedexosomes, FBS was spun at 100,000 g for 2 hours to remove exosomesbefore the experiment. The recovery of exosomes was estimated bymeasuring the protein concentration using the Bradford assay and byNanoparticle Tracking Analysis (NTA). The obtained exosomal fraction wasre-suspended in PBS (500 μl, 1 mg/mL total protein), and characterizedfor size and polydispersity.

Loading of Exosomes: Four approaches for catalase incorporation intoexosomes were evaluated: the incubation at RT with or without saponin(Method I), freeze-thaw cycles (Method II), sonication (Method III), andextrusion (Method VI). For Method I, naive exosomes released from Raw264.7 macrophages were diluted in PBS to a concentration 0.15 mg/mL oftotal protein, then catalase solution in PBS (0.5 mg/mL) was added to250 μl of exosomes to the final concentration 0.1 mg/mL total protein,and incubated at RT for 18 hours. In case of a saponin treatment, amixture of catalase and exosomes was supplemented with 0.2% saponin andplaced on shaker for 20 min at RT. For Method II, the catalase solutionwas added to exosomes as described above, incubated for 30 min, thenrapidly freezed at −80° C., and thawed at RT. The freeze-thaw cycle wasrepeated three times. For Method III, the catalase mixture with exosomeswas sonicated (500 v, 2 kHz, 20% power, 6 cycles by 4 sec pulse/2 secpause), cooled down on ice for 2 min, and then sonicated again usingQsonica Sonicator Q700 (Fisher Scientific, Hampton, N.H., USA). ForMethod IV, catalase mixture with exosomes was extruded (×10 times)through Avanti Lipids extruder (Avanti Polar lipids Inc., Alabaster,Ala., USA) with 200 nm-pores diameter. Loaded with catalase exosomeswere purified from free catalase by gel-filtration chromatography withSepharose 6 BCL (Sigma-Aldrich).

Characterization of different exoCAT formulations by (Dynamic LightScattering) DLS, (Atomic Force Microscopy) AFM, Nanoparticle TrackingAnalysis (NTA), and Hyperspectral microscopy: The effective hydrodynamicdiameter of empty exosomes, or exosomes loaded with catalase wasmeasured by DLS using the ZetaPlus' Zeta Potential Analyzer (BrookhavenInstruments, Santa Barbara, Calif., USA) equipped with a 35 mW solidstate laser (658 nm laser) as described in (Bronich et al., J. Amer.Chem. Soc. 122:8339 (2000); Vinogradov et al., Colloids SurfacesB-Biointerfaces 16:291 (1999)). The size, distribution, and number ofparticles for various exosomal formulations were also examined by NTA.For this purpose, exoCAT formulations were prepared at concentration0.01 mg/mL, and evaluated using NanoSight 500, Version 2.2 (Wiltshire,United Kingdom). The morphology of exoCAT aggregates was investigated byAFM. Different exoCAT formulations were prepared in 50 mM phosphatebuffer, pH 7.4 at total protein 10 μg/mL. A drop of the sample wasplaced on a glass slide, and dried under an argon flow. The AFM imagingwas operated as described earlier (Zhao et al., Nanomedicine (Lond) 6:25(2011)).

ExoCAT formulations were further characterized by Hyperspectralmicroscopy (CytoViva Inc., Auburn, Ala., USA). The hyperspectral imagesand the corresponding hyperspectral data were captured using an OlympusBX43 research grade optical microscope equipped with the patentedCytoViva advanced dark field illumination system and diffraction gratinghyperspectral imaging system (CytoViva Inc.). A 100× oil iris 0.6-1.30NA objective was utilized. For the mean spectral comparison, data wascaptured from multiple pixels within multiple exosome particle areas ofeach sample. The mean spectrum from each sample was calculated using theCytoViva customized ENVI Hyperspectral Image Analysis software.

Manufacture of gold nanoparticles and imaging of nanoparticle-loadedexosomes by Transmission Electron Microscopy (TEM): Gold nanoparticleswere prepared by mixing of 25 mL HAuCl4 (0.5 mM) TRIS solution (pH 10)with 25 mL Pluronic® block copolymer F127 (10 mM) solution. The mixturewas incubated at 55° C. for 2 hours and the obtained nanoparticles wereseparated by centrifugal filtration at 1500 RPM using a filter with 100kDa cut off. Effective hydrodynamic diameter and zeta-potential of goldnanoparticles were measured by photon correlation spectroscopy using‘ZetaPlus’ Zeta Potential Analyzer (Brookhaven Instruments). The averagediameter was 10.3±0.2 nm, the polydispersity index (PDI) value was0.06±0.002 nm. For TEM evaluations, a drop of isolated exosomal fractionwith incorporated by sonication gold nanoparticles was placed onFormvar®-coated copper grid (150 mesh, Ted Pella Inc., Redding, Calif.,USA). The dried grid containing exosomes were stained with vanadylsulfate and visualized using a Philips 201 transmission electronmicroscope (Philips/FEI Inc., Briarcliff Manor, N.Y., USA).

Poly(lactic-co-glycolic acid) (PLGA) particles preparation: PLGAnanoparticles were prepared by modification of a w/o/w double emulsionmethod (Giovagnoli et al., AAPS Pharm Sci Tech 5:e51 (2004)). Briefly,3.2 mL of 5% polyvinyl alcohol (PVA) was added to 100 mL of dH₂O₂ toform a w/o emulsion. In parallel, 0.35 g PLGA polymer was dissolved in 3mL dichloromethane, and 2 μmol DIL was added to the solution. Aftervigorous stirring, the PLGA emulsion was injected into 50 mL of 5% PVAsolution under stirring (1500 rpm, at 4° C.) to form a primary w/o/wdouble emulsion. Then, the double emulsion was poured into 500 mL ofdeionized water and maintained at 4° C. In order to evaporate theorganic solvent, the temperature was slowly increased up to 20° C.during two hours. The resulting nanoparticles were centrifuged for 30minutes at 4000 g, washed with deionized water, and lyophilized. Theaverage particle size measured by Malteasizer DLS was 317.5+1.94 nm withPDI of 0.113.

Preparation of liposomes: Liposomes were prepared by reverse phaseevaporation method. Briefly 2 mg of phospholipids (95 molar % ofphosphatidyl choline and 5% of poly(ethyleneglycol)-1,2-distearoyl-sn-glycero-3-phosphoethanolamine (PEG-PE)) weredissolved in 6 ml of chloroform: diisopropyl ether 1:1 mixture. Then 1ml of 5 mM calcein solution in PBS filtered through 450 nm syringefilter was added to the mixture. Mixture was intensively vortexed andbath sonicated to form stable emulsion. Organic solvents were evaporatedon rotary evaporator forming the liposome aqueous dispersion. 200-250 μlof Millipore water can be added at this point to the mixture in casesome part of water was also evaporated. Evaporation was continued to getalmost clear dispersion. Then volume was adjusted to 1000 μl by additionof small amount of water. Dispersion was vortexed and bath sonicated toget clear solution. Liposomes were sequentially extruded 21 timesthrough 200 nm polycarbonate filters using a hand extruder (Avanti).Liposomes were purified through a Sepharose CL4B column to remove notencapsulated fluorophore. Volume of the sample was doubled after columnseparation. Calcein loaded liposomes were used within 24 h after columnseparation.

Western blot analysis: Western blot technique was applied to evaluateloading efficiency for different exoCAT formulations. Proteinconcentrations were determined using BCA kit (Pierce Biotechnology,Rockford, Ill., USA). The catalase protein bands were detected withprimary rabbit polyclonal anti-catalase antibodies (Santa Cruse, Calif.,USA; 1:200 dilution), and secondary horseradish peroxidase(HRP)-conjugated goat anti-rabbit Ig-HRP (Santa Cruse; 1:2500 dilution).The protein bands were visualized by chemiluminescent substrate (PierceBiotechnology) and quantitated using ImageJ software (NIH, Bethesda,Mass., USA) (Batrakova et al., Bioconjug. Chem. 18:1498 (2007)). Tocorrect for loading differences, the levels of proteins were normalizedto the constitutively expressed in exosomes TSG101 protein. The TSG101levels were visualized by TSG101 monoclonal antibodies, Abcam(Cambridge, Mass., USA).

Enzymatic activity of catalase loaded into exosomes: The loadingefficiency for different exoCAT formulations was assessed by catalaseenzymatic activity using hydrogen peroxide decomposition assay (Zhao etal., Nanomedicine (Lond) 6:25 (2011)). For this purpose, differentexoCAT formulations were incubated with pronase (0.1-0.2 mg/mL) for 3hours at 37° C. Following the incubation, the aliquots were subjectedfor catalytic activity assessment as described above. The same assay wasused to examine the preservation of catalase enzymatic activity inexosomes against proteases degradation. Stability of catalase wasexpressed in the residual activity vs. initial activity of catalase.

Exosomal uptake in PC12 cells: PC12 neuronal cells is a common model forin vitro evaluation of drug neuroporotective effects (Tan et al.,Neurochem. Res. 38:512 (2013)). Exosomes (230 μg total protein/mL) weresubjected to various procedures (incubation at RT, freeze/thaw cycles,or sonication), and then stained with DIL (2 μmol). PC12 cells wereseeded into 96-well plate (50,000 cell/well), cultured for three days,and then incubated with different DIL-labeled exoCAT for various times.Following the incubation, the cells were washed three times withice-cold PBS, and solubilized in Triton X100 (1%). Fluorescence in eachsample was measured by Shimadzu RF5000 fluorescent spectrophotometer(λ_(ex)=540 nm, λ_(em)=565 nm). The amount of exosomes accumulated inneuronal cells was normalized for the total protein content andexpressed as a number of exosomes per mg of the protein as means±S.E.M.(n=8). All exoCAT formulations were prepared at the same level offluorescence, and a separate calibration curve was used for each exoCATformulation.

In vitro confocal microscopy studies: Raw 264.7 macrophages (20×10⁶cells/flask) were cultured for three days in DMEM supplemented with 10%FBS, then concomitant media was collected, and exosomes were isolated bygradient centrifugation as described above. The isolated exosomes (100μg/mL total protein) were sonicated, labeled with DIL (2 μmol), andincubated with PC12 cells grown on chamber slides (1×10⁵ cells/chamber)for various time intervals (Batrakova et al., Bioconjug. Chem. 16: 793(2005)). Following the incubation period, the cells were washed, fixed,and stained with rabbit anti-PGP9.5 antibodies (green, Abcam, #10404,1:500 dilution) for actin micro-filaments, and a fluorescent stain,4′,6-diamidino-2-phenylindole (DAPI) for nuclei prior to the imaging.Accumulation of fluorescently-labeled exosomes was visualized by aconfocal fluorescence microscopic system ACAS-570 (Meridian Instruments,Okimos, Mich., USA) with argon ion laser (excitation wavelength, 488 nm)and corresponding filter set. Digital images were obtained using the CCDcamera (Photometrics).

Amplex Red dye fluorescence assay: Raw 264.7 macrophages seeded in96-well plates (0.1×10⁶ cells/well) were stimulated with INF-γ (2 μg/mL)and LPS (200 ng/mL) for 4 hours to induce ROS production. Non-activatedcells were used as controls. ExoCAT obtained by sonication inKrebs-Ringer buffer (145 mM NaCl, 4.86 mM KCl, 5.5 mM glucose, 5.7 mMNaH₂PO₄, 0.54 mM CaCl2), 1.22 mM MgCl₂, pH 7.4) were supplemented withAmplex Red Dye stock solution (10 U/mL HRP and 10 mM Amplex Red), addedto the activated macrophages, and the decomposition of ROS was measuredby fluorescence at λ_(ex)=563 nm, λ_(em)=587 nm as described (Batrakovaet al., Bioconjug. Chem. 18:1498 (2007)). The effect of the same amountof empty exosomes (1.4×10¹/mL exosomes), or catalase alone (3,652 U/mL)on ROS decomposition was evaluated in the control experiments.

Cell viability assay: The protection of PC12 cell by exoCAT prepared bysonication was assessed by MTT assay. For this purpose, PC12 cells(1×10⁵ cells/mL) were seeded into a 96-well plate and allowed to attachovernight. Then, the cells were exposed to 200 μM 6-OHDA and differentexoCAT formulations, or catalase alone, or empty exosomes for fourhours. Following the incubation, the cells were washed 3 times withice-cold PBS, and incubated with the corresponding exoCAT formulations,or catalase alone, or empty exosomes for another 24 hours. Following thetreatment, 20 μL MTT (5 mg/mL) was added into each well. After 3 hoursof incubation at 37° C., the medium containing MTT was removed; and 100μL DMSO was added into each well to dissolve the purple MTT formazan.Absorbances were read at λ=570 nm by a microplate reader, and cellviability was expressed as a percentage of viable cells in the treatedgroups compared to the untreated control group.

Animals: C57BL/6 female mice (Charles River Laboratories, Durham, N.C.,USA) eight weeks of age were treated in strict accordance with therecommendations in the Guide for the Care and Use of Laboratory Animalsof the National Institutes of Health. The protocol was approved by theCommittee on the Ethics of Animal Experiments of the University of NorthCarolina at Chapel Hill. All surgery was performed under sodiumpentobarbital anesthesia, and all efforts were made to minimizesuffering. The animals were kept five per cage with an air filter coverunder light- (12-hours light/dark cycle) and temperature-controlled(22±1° C.) environment. All manipulations with the animals wereperformed under a sterilized laminar hood. Food and water were given adlibitum.

Biodistribution of exosomes in mouse brain with inflammation: C57BL/6mice (n=4) were stereotactically injected with 6-OHDA solution (10 μg6-OHDA in 0.9% NaCl with 0.02% ascorbic acid), flow rate of 0.1 μL/mininto the striatum (AP: +0.5; L: −2.0 and DV: −3.0 mm) (Zhao et al., J.Nanomed. Nanotechnol. S4 (2011)). Twenty one days later (at the peak ofinflammation), mice were intranasally (i.n.) or intravenously (i.v.)injected with fluorescently-labeled exosomes (2.4×10¹⁰ exosomes/mouse).Four hours later, mice were sacrificed, perfused, and the brain slideswere examined by confocal microscopy. 6-OHDA-intoxicated mice injectedwith PBS were used as controls. Nuclei were labeled with DAPI. Toexamine which type of cells accumulates exosomes in the brain, aco-localization study with cell-specific markers was carried out. Forthis purpose, the brain slides were co-stained with: primary (1) rabbitpolyclonal antibodies to neurons, AntiNeuN (ab128886, Abcam, 1:500dilution), or (2) anti-tyrosine hydroxylase (TH) rabbit antibodies toTH-neumons (Calbiochem, 1:1000 dilution), or (3) rabbit anti CD146 toendothelial cells (ab75769, Abcam, 1:250 dilution), or (4) rabbitanti-GFAP antibodies to astrocyte marker (ab7260, Abcam, 1:500dilution), and secondary antibodies, donkey anti-rabbit IgG H&L Alexa555 (abcam ab150074, Abcam, 1:500 dilution). All slides werepermeabilized for 60 min in 0.1 M citrate buffer pH6.0 and 0.05% Tween20, washed 3×5 min with 0.05% Tween 20 in PBS, blocked for 30 minuteswith PBS and 5% Normal Donkey Serum+0.05% Tween 20, and stained withprimary antibody at stated dilution overnight at 4° C. Following theincubation, slides were washed 3×5 minutes/wash in PBS/Tween, andstained with secondary antibodies for one hour at room temperature.Then, the slides were washed 3×PBS/Tween 5 min/wash ddH2O, and coveredusing Vectashield Hardset mounting media with Dapi. The images wereexamined by a confocal fluorescence microscopic system ACAS-570 andcorresponding filter set.

Immunohistochemical and stereological analyses: 6-OHDA-intoxicated mice(n=7) were treated via i.n. administration with PBS, or catalase alone(1.2×10⁹ exosomes with 408.44 U catalase/mouse×2 in 10 μl PBS, ten timesevery other day), or exoCAT loaded by sonication or saponinpermeabilization with the same amount of catalase (1.2×10⁹exosomes/mouse×2 in 10 μl PBS), or the same amount of empty exosomes 48hours after the intoxication (10 times every other day). Two controlgroups of healthy non-intoxicated animals were i.c. injected with PBS,and then 48 hours later were i.n. injected with PBS, or empty exosomes.Twenty one days later, animals were sacrificed, perfused; brains wereremoved, washed, post-fixed, and immunohistochemical analysis wasperformed in 30 μm thick consecutive coronal brain sections as described(Brynskikh et al., Nanomedicine (Lond) 5:379 (2010)). For the detectionof microglia activation, tissue sections were incubated with primarymonoclonal rat anti-mouse anti-CD11b antibodies (1:500 dilution), andsecondary biotinylated goat anti-rat antibodies (Vector Laboratories,Burlingame, Calif., 1:200 dilution). Thus, activated microglia withinthe SNpc will exhibit a more amoeboid morphology with sent out branches,compared to ramified barely visible resting microglia. In addition,levels of astrocytosis were assessed in the ventral midbrain region byfluorescent analysis of glial fibrillary acidic protein (GFAP)expression. For the GFAP staining, tissue sections were permeabilizedwith 0.01% Triton X-100 in TBS for 30 minutes and blocked for 1 hourwith 10% normal goat serum (NGS, Vector Laboratories Inc., Burlingame,Calif.), then incubated with rabbit anti-GFAP primary polyclonalantibodies ab7260 (AbCam, Cambridge, Mass.) 1:100 dilution for 16 hoursat 4° C. Tissue slides were incubated with goat anti-rabbit Alexa Fluor647 secondary antibodies (Invitrogen; 1:200 dilution) for 1 hour, andmounted on slides. Immunoreactivity was evaluated by fluorescentanalysis using confocal microscope Zeiss 510 Meta Confocal LaserScanning Microscope (Jena, Germany), and ImageJ software (NIH, Bethesda,Mass., USA). For the assessment of neuroprotective effects, a THstaining was used to quantitate numbers of DA neurons (Tieu et al., J.Clin. Invest. 112:892 (2003)). The total number of TH-positive DAneurons was counted by using the optical fractionator module inStereoInvestigator software (MicroBrightField, Inc., Williston, Vt.)(Brynskikh et al., Nanomedicine (Lond) 5:379 (2010)).

Apomorphine Test: C57BL/6 mice were i.c. injected with 6-OHDA (n=7).Healthy mice i.c. injected with PBS were used as a control (Keshet etal., J. Comp. Neurol. 504:690 (2007)). Starting from 48 hours afterintoxication, mice were i.n. injected with PBS, or exoCAT obtained bysaponin permeabilization every other day for two weeks. Twenty one dayslater, the animals were injected with apomorphine (0.05 mg/kg, s.c.) androtations were scored every 10 min for 90 min as described (Papathanouet al., Eur. J. Neurosci. 33:2247 (2011)).

Statistical analysis: For all the experiments, data are presented as themean±S.E.M. Tests for significant differences between the groups wereperformed using a t-test or one-way ANOVA with multiple comparisons(Fisher's pairwise comparisons) using GraphPad Prism 5.0 (GraphPadsoftware, San Diego, Calif., USA). A minimum p value of 0.05 was chosenas the significance level.

Results

Manufacture of exosomal formulations of catalase (exoCAT): Catalase wasincorporated into exosomes using different methods: a) incubation at RTwith or without of saponin permeabilization; b) freeze/thaw cycles; c)sonication, and d) extrusion procedures. The last two methods wereutilized to cause a reformation/deformation of exosomes in the presenceof catalase. The obtained exoCAT formulations were purified fromnon-incorporated catalase by a gel-filtration chromatography withSepharose 6BCL as described in Materials and Methods section.

According to the western blot analysis, the amount of catalase loadedinto exosomes increased in the row: the incubation at RT<freeze/thawcycle <sonication≅extrusion (FIG. 1A). These results were confirmed bycatalytic activity of the enzyme (FIG. 1B). ExoCAT obtained bysonication and extrusion showed the highest catalytic activity, followedby exoCAT obtained by freeze/thaw cycles, and then the incubation at RT(without saponin permeabilization). The incubation of catalase withexosomes at RT resulted in the lowest loading efficiency (4.9±0.5%, n=4)among all evaluated methods. Nevertheless, when exosomes werepermeabilized with saponin, catalase loading efficiency significantlyincreased (18.5±1.3%, p<0.05). Furthermore, sonication and extrusionprocedures resulted in the most efficient enzyme incorporation(26.1±1.2% and 22.2±3.1%, respectively). We hypothesized that aformation of transient pores or even reformation of exosomes uponsonication and extrusion allowed diffusion of catalase from thesurrounding media into exosomes. The freeze/thaw cycles technique gavesomewhat intermediate values of loading efficiency (14.7±1.1%).Regarding the yield of the catalase formulations, about 98% of exosomeswere recovered upon all loading methods. Noteworthy, catalase structurewas stabilized upon incorporation into exosomes. No loss of catalaseenzymatic activity was detected in exoCAT upon sonication, whilecatalase alone was significantly deactivated in the same conditions(down to 14%).

The release of catalase from pre-loaded exosomes was evaluated byenzymatic activity using dialysis membranes with a cut off 2000 KDa(FIG. 1C). The fastest release was observed for the formulation obtainedby incubation at RT without saponin (FIG. 1C). In contrast, a prolongedand sustained release was recorded for exoCAT obtained by sonication;less than 40% of catalase was released over 24 hours. Taken together,the sonication of exosomes in the presence of catalase resulted in thehigh loading efficiency, and sustained release of enzymatically-activecatalase. In particular, each mg of exoCAT obtained by sonicationcontained approximately 1,376±64.1 U of catalase activity in 4×10¹¹exosomes/mL.

Characterization of exoCAT formulations: The size of catalase-loadedexosomes was determined by DLS and NTA techniques (Table 1). Particlesof naked catalase showed small size (9.5 nm) with low polydispersityindex (PdI), which was close to the theoretical diameter (10.5 nm) of asingle protein globule calculated from the molecular mass of the enzyme(Papadopoulos et al., Biophys. J. 79:2084 (2000)). An average diameterof empty exosomes was around 100 nm with a relatively highpolydispersity (Table 1). The incubation of catalase with exosomes at RT(with or without saponin) did not significantly alter their size.However, freeze/thaw cycles, extrusion, and sonication of exosomesresulted in the significant size increases, especially, in the presenceof catalase (Table 1). Overall, both DLS and NTA analyses indicate thesize of the obtained exoCAT formulations was in the range of 100-200 nm.This suggests that the relatively small catalase-loaded nanoparticlesmight enter the target cells by endocytosis.

TABLE 1 Size of catalase exosomal formulations obtained by DLS andNTA^(a) (^(a) Statistical significance is compared to the diameter ofnaïve exosomes alone and shown by symbols: p < 0.05 (*), or p < 0.005(**) DLS Formulation D_(eff) (nm) PdI NTA (nm) Catalase alone 9.5 ± 0.10.10 n/a exosomes alone 100.5 ± 13.5 0.20 99.5 ± 11.2 exoCAT, mixture108.0 ± 14.3 (ns) 0.35 100 ± 16.3 (ns) exoCAT, mixture & 110.5 ± 23.1(ns) 0.35 111 ± 7.8 (ns) saponin exosomes, freeze/thaw 147.0 ± 10.0 (*)0.48 125 ± 17 (*) exoCAT, freeze/thaw 158.0 ± 11.0 (*) 0.48 130 ± 11 (*)exosomes, sonicated 179.0 ± 10.6 (*) 0.30 150 ± 8.2(*) exoCAT, sonicated183.7 ± 13.8 (**) 0.25 162.4 ± 6.1 (**) exosomes, extruded 134.0 ± 7.5(*) 0.25 130 ± 7.5 (*) exoCAT, extruded 154.8 ± 11.0 (*) 0.29 149.4 ±3.3 (*)

Based on the data from NTA experiments and evaluations of catalaseactivity, about 940±15 catalase molecules per exosome were incorporatedby sonication. Noteworthy, exosomal formulations were stable at RT overa week; no changes in size and/or catalase activity were recorded.Furthermore, the restitution of lyophilized exoCAT in water solutionsdid not alter the size, and activity of exosomal formulations.

The AFM images revealed considerable differences in the morphology ofexoCAT formulations (FIG. 1D). Naïve exosomes isolated from Raw 264.7macrophages, as well as exosomes incubated with catalase at RT, orobtained by extrusion procedures have a round morphology. Particles ofexoCAT formulation manufactured by freeze-thaw cycle were considerablylarger in size consisting of several dozen of smaller exosomes, probablydue to the aggregation. The AFM images of sonicated exoCAT demonstratednon-spherical associates with a variety of shapes (FIG. 1D).

Next, the loading of catalase into exosomes was confirmed byhyperspectral microscopy. This technique enables optical observation,spectral characterization, and mapping of nanoscale materials in a widerange of biological and material-based environments. FIGS. 2A-2C showrepresentative hyperspectral images of exosomes loaded with catalase bysonication (FIG. 2A), and empty exosomes sonicated at the sameconditions (FIG. 2B). The measurements illustrate a narrowing of thespectral response of the loaded versus the unloaded exosomes (FIG. 2C).This suggests that significant alterations/perturbations occur uponcatalase incorporation into exosomes. The incorporation of catalase intoexosomes significantly improved its enzymatic stability against proteasedegradation (FIG. 3 ). In accordance with the loading efficiency (FIG.1A-1B), and release kinetics (FIG. 1C), the stability of catalase wasincreased in the row: incubation at RT without saponin <freeze/thawcycles <sonication (FIG. 3 ). Altogether, this indicates that catalasewas not only associated with the surface of exosome, but was alsoincorporated into them.

Accumulation and therapeutic efficacy of exoCAT in target neuronal cellsin vitro: The ability of nanocarriers to deliver the drug payload intotarget cells is crucial for the therapeutic efficiency of exosomalformulations. First, we examined whether manipulations with exosomesaffect their transport into target cells in vitro. Exosomes weresubjected to various loading procedures (incubation at RT, freeze/thawcycles, or sonication), labeled with lipophilic fluorescent dye, DIL,and then incubated with PC12 cells. Striking differences in accumulationlevels were recorded (FIG. 4A). In spite of their large size, sonicatedexosomes were taken up at considerably greater levels than thosesubjected to freeze/thaw cycles, or incubation at RT. This suggestssuperior interactions of sonicated exosomes than other exosomalpreparations with cellular plasma membranes. We speculate that areorganization of exosomes upon sonication may result in the exposure ofhydrophobic parts of the cellular lipid bilayers or incorporatedproteins that improve their interactions with plasma membranes of targetcells. Next, confocal images confirmed a profound accumulation ofsonicated DIL-labeled exosomes in PC12 cells (FIG. 4B). The exosomeswere efficiently internalized into neurons followed 3-hour incubation(FIG. 4B-I), filled the entire neuronal body and build up on the plasmamembranes at later time points (FIG. 4B-II). The unparalleledaccumulation of exosomes in target cells was even more evident incomparison with the considerably lower uptake of commonly used for thedrug delivery polymer-based PLGA nanoparticles (100 nm, FIG. 4B-III), orliposomes (FIG. 4B-IV) that were applied at the same level offluorescence. These nanocarriers (PLGA nanoparticles and liposomes) wereutilized for the brain delivery of L-DOPA to treat PD.

Given the efficient accumulation of exosomes in PC12 neurons, wehypothesized that exosomes with incorporated catalase may deliver asubstantial amount of the enzyme into target neuronal cells, and as aresult, provide a superior neuro-protective activity against oxidativestress. To test this hypothesis, the effect of exoCAT formulations onneuronal survival was evaluated in PC12 cells pre-treated with 6-OHDA torecapitulate components of PD neurodegeneration in vitro. Following the6-OHDA pre-treatment, the PC12 cells were supplemented with variousexoCAT formulations, and the neuronal survival was evaluated by MTT test(FIG. 4C). As expected, exoCAT prepared by sonication and extrusiondemonstrated greater neuroprotective activity than exosomes loaded withcatalase by freeze/thaw cycles or incubation at RT, probably, due to thefacilitated exoCAT accumulation, and/or protection of catalase againstdegradation in exosomal carriers. Noteworthy, permeabilization ofexosomes by saponin upon loading with catalase significantly increasedneuroprotection effect produced by this formulation (FIG. 4C). Catalasealone, as well as empty exosomes did not protect PC12 cells at theseexperimental conditions.

Next, exoCAT obtained by sonication was evaluated for the ability toeliminate ROS produced by activated macrophages in vitro (FIG. 4D). Inthis experiment, macrophages pre-incubated with a mixture of LPS (100ng/mL) and TNF-α (100 ng/mL) were utilized as a model of activatedmicroglia in the PD brain. The activation of macrophages resulted in thesignificant increase in ROS production, whereas the addition of exoCATconsiderably decreased hydrogen peroxide levels (FIG. 4D). Interesting,empty exosomes also decreased ROS levels in activated macrophages downto the levels of the control non-activated cells, although this effectwas less significant than the effect of exoCAT. This indicates thatexosomes by themselves (probably, their internal content) have acapacity to deactivate free radicals. This result is consistent with thestudies demonstrating protection effects of exosomes against myocardialischemia/reperfusion injury (Lai et al., Stem Cell Res. 4:214 (2010)).Altogether, these data suggests that exoCAT can be a useful tool for ROSdeactivation and neuronal protection against oxidative stress.

Transport of exosomes into mouse brain with inflammation: To visualizethe ability of exosomes to target and deliver their payload to inflamedbrain tissues, confocal imaging studies were conducted in a PD mousemodel. To induce brain inflammation, C57BL/6 mice were intracranially(i.c.) injected with 6-OHDA into SNpc. Twenty one days later (at thepeak of inflammation), mice were injected with DIL-labeled exosomes(2.4×10¹⁰ exosomes/20 μL/mouse) through intranasal (i.n.) (FIG. 5B), orintravenous (i.v.) (FIG. 5C) routes. Mice i.n. injected with PBS wereused as controls (FIG. 5D). Four hours later, mice were euthanized,perfused, and brain slides were examined by confocal microscopy. Nucleiwere stained with DAPI (blue). The images revealed a wide distributionof exosomes throughout the brain, in particular, cerebral frontalcortex, central sulcus, and cerebellum (FIG. 5A). The amount of exosomesdelivered upon the i.n. administration was greater (FIG. 5B) than thosedelivered through i.v. injection (FIG. 5C). Confocal images showeddiffuse fluorescent staining throughout the brain tissues along with thestained vesicular compartments localized predominantly in perinuclearregions (shown by arrows). No fluorescence was found in control micewith the PBS injection (FIG. 5D). As such, i.n. route of administrationwas selected for the further evaluations of exoCAT therapeutic effects.

Catalase-loaded exosomes protect SNpc neurons against oxidative stressin mice with acute brain inflammation: The neuropathology of PD includesbrain inflammation, microglial activation, and secretion of neurotoxins,such as ROS, all of which contribute to neurodegeneration anddegradation of motor function (Stone et al., Antioxid. Redox Signal,(2009)). We posit that the successful brain delivery of catalase willreduce neuroinflammation resulting in improved disease outcomes. Forthis purpose, C57BL/6 mice were stereotactically injected with 6-OHDAinto SNpc, and 48 hours later, mice were i.n. injected with exoCAT(1.2×10⁹ exosomes with catalase activity 408.44 U/10 μL/mouse into eachnostril, 10 times every other day), or the same amount of catalasealone.

Two exoCAT formulations were evaluated; catalase-loaded exosomes bysonication, or permeabilization with saponin at RT (n=7). Miceintoxicated with 6-OHDA, and then i.n. injected with PBS were used ascontrol animals with brain inflammation (PD mice). Non-intoxicatedanimals i.c. injected with PBS were used as healthy controls. Toevaluate the effect of empty exosomes in healthy brain, another controlgroup of healthy animals was i.c. injected with PBS, and then emptyexosomes. Twenty-one days following administration of the testformulation, the mice were sacrificed, perfused with paraformaldehide(PFA), and brains harvested. Brain slides were stained with antibodiesto activated microglia (FIGS. 6A-6G), astrocytes (FIGS. 7A-7C), orTH-expressing DA neurons (FIGS. 8A-8G). The quantification of theobtained results for anti-inflammatory and neuroprotective effects ispresented on FIGS. 6F and 8F, respectively.

6-OHDA injections produced substantial brain inflammation signified byup-regulated expression of CD11b by microglia within the SNpc thatexhibited a more amoeboid morphology (FIG. 6C) than ramified microgliain PBS-treated mice (FIG. 6A). Furthermore, the 6-OHDA-mediatedintoxication resulted in the complete degeneration of DA neurons in theipsilateral hemisphere SNpc (FIG. 8C, arrow). The anti-inflammatoryeffect of exoCAT was demonstrated by the significant (p<0.005) reductionin microgliosis as measured by CD11b expression (FIGS. 6D, 6E, 6G) anddecrease in astrocytosis as demonstrated by GFAP levels (FIGS. 7A-7C).Furthermore, i.n. administration of exoCAT resulted in a 3-fold increasein survived DA neurons (FIGS. 8D, 8E, 8G) compared to the control6-OHDA-treated mice injected with PBS (FIGS. 8C, 8G). Theneuroprotection was greater in the animal group treated with exoCATobtained by permeabilization with saponin (FIGS. 8E, 8G) than withexoCAT loaded by sonication (FIGS. 8D, 8G). Not surprisingly, freecatalase was not effective in decreasing inflammation or providingneuroprotection in 6-OHDA-intoxicated mice (FIGS. 6E and 6E).

Next, we investigated the effect of exoCAT formulation obtained bysaponin permeabilization in apomorphine test. Mice intoxicated with6-OHDA and treated i.n. with PBS showed 150±11 rotations per minute. Incontrast, mice intoxicated with 6-OHDA and then treated i.n. with exoCATas described above have significantly less rotations (26.1±3.1 perminute). Noteworthy, non-intoxicated healthy controls did not rotate atall.

Finally, we investigated possible toxic effect of exosomal carriersalone. No effect of empty exosomes on the microglial activation ornumber of DA neurons was found in healthy mice (FIGS. 6B and 8B)compared to the healthy PBS-treated controls (FIGS. 6A and 8A,respectively) suggesting absence of neurotoxic effects of exosomalcarriers in the brain. This result was confirmed in in vitro model ofprimary cortical or DA neurons isolated from mouse pups. Thus, a 48-hourexposure of primary neurons to exosomes released from macrophages didnot affect neuronal survival (FIG. 9 ). Overall, these resultsdemonstrate that exosomal formulations of catalase may be useful for PDtherapies.

Co-localization of exosomes with various types of cells in the brain: Toassess which cell type in the brain accumulates exosomes, brain slideswere co-stained with different cell markers (FIG. 10 ). Interesting,exosomes were mostly co-localized with neurons, microglia and partiallywith endothelial cells (FIG. 10 ). Noteworthy, along with distinctendosomal compartments filled with exosomes, a diffuse exosomal stainingwas evident throughout all brain tissues. It is likely theexosome-mediated delivery of catalase to activated microglia,astrocytes, and neurons in the inflamed brain may result in ROSdegradation and neuroprotection in PD patients.

Discussion

Currently, there are no treatments that halt or reverse the course ofPD, and only palliative therapies, such as replacement strategies formissing neurotransmitters, exist. The inability of most potenttherapeutics, and especially therapeutic proteins, to cross the BBBfollowing systemic administration dictates the necessity to developunconventional, clinically applicable drug delivery systems. In thisrespect, biocompatible vehicles, such as exosomes, may help to solvethis challenging task.

Oxidative stress has long been implicated in the process ofneurodegeneration seen in Parkinson's patients. Indeed, the pathogenesisof PD is associated with a lack of the natural antioxidants catalase,glutathione and superoxide dismutase in the midbrain region,specifically, in the SNpc (Jin et al., Biochim. Biophys. Acta 1842:1282(2014)). It was demonstrated that cells of the immune system, andparticularly microglia, release pro-inflammatory cytokines in responseto different stress conditions (Lucin et al., Neuron 64:110 (2009))leading to neuronal demise (Chan, J. Cereb. Blood Flow Metab. 21:2(2001)). Antioxidants can inhibit inflammatory responses and protectdopaminergic neurons as reported in laboratory and animal models of PD.In particular, catalase, one of the most efficient antioxidants found innature, has been shown to rescue primary cerebellar granule cells in invitro models of PD (Prasad et al., Curr. Opin. Neurol. 12:761 (1999);Gonzalez-Polo et al., Cell Biol. Int. 28:373 (2004)). Several clinicalstudies have assessed the therapeutic efficacy of low molecularantioxidants for PD therapy. Unfortunately, the results of theseinvestigations have been disappointing due to the drug poorpharmacokinetics and inability to penetrate the BBB (Pappert et al.,Neurology 47: 1037 (1996)). Thus, the development of novel approachesfor brain delivery of antioxidants, and in particular redox enzymes, isof utmost importance.

We report here the development of a new exosomal-based technology forcatalase CNS delivery to treat PD. Catalase is a large protein (MW 240K) that is susceptible to deactivation and rapid degradation. Therefore,different techniques for catalase loading into exosomes were evaluated:incubation at RT with or without saponin permeabilization, freeze/thawcycles, sonication, or extrusion. Our data indicate the size,morphology, loading efficiency, and stability of exoCAT formulationsstrongly depended on the method of preparation. Thus, the extensivereformation and reshaping of exosomes upon sonication and extrusionenabled catalase diffusion across relatively tight and highly structuredlipid bilayers and resulted in the high loading efficiency of exosomalcarriers. Notably, these approaches for incorporation into exosomes arenot specific only for proteins, but can be applied to other therapeuticand imaging agents. Thus, TEM studies indicated that a substantialamount of gold nanoparticles with the diameter (10.3±0.2 nm) can be alsoincorporated/associated with exosomes by sonication (FIG. 11 ).Interesting, similar to the sonicated exoCAT (FIG. 1D),nanoparticles-loaded exosomes showed non-spherical morphology with avariety of shapes (FIG. 11 ). Indeed, it should be taken intoconsideration that the disruption of the exosomes integrity duringsonication or extrusion procedures may alter their immune-privilegedstatus, and therefore, make them visible for the MPS.

Noteworthy, saponin treatment also increased loading of catalase intoexosomes. Saponin is the efficient permeabilization agent for cellularplasma membranes (Jamur et al., Meth. Mol. Biol. 588:63 (2010)). Wehypothesized that similar to the whole cells, saponin may selectivelyremove membrane-bound cholesterol of exosomes, creating holes/pores inthe exosomal lipid bilayers and therefore, promoting catalaseincorporation. Overall, exoCAT obtained by sonication and extrusion, aswell as saponin treatment showed the high loading efficiency,preservation of catalase enzymatic activity against proteasesdegradation, and prolonged and sustained release.

Regarding the delivery of incorporated therapeutics to the target cells,this study demonstrated the extraordinary ability of exosomes tointeract with target cells and deliver their “payload” into neighboringneurons. Confocal images revealed fluorescently-labeled exosomes wereadhering and overflow neuronal cells in abundance. Indeed, comprising ofcellular membranes exosomes should have an exceptional ability tointeract with target cells. Furthermore, exosomal surface is rich withtetraspanins and integrins (Rana et al., Int. J. Biochem. Cell Biol.44:1574 (2012)) that enable the efficient attachment to the plasmamembrane of target cells. As a result, exosomes accumulated inconsiderably greater levels in PC12 cells than PLGA nanoparticles thathave been used as common nanocarriers for PD therapy (Danhier et al., J.Control. Release 161:505 (2012)) or liposomes (Spuch et al., J. DrugDelivery 2011, 469679 (2011)). Interesting, the accumulation levelsvaried for different exosomal preparations. In particular, sonicatedexosomes showed the greatest uptake in neurons compared to exosomesincubated at RT, or aggregates obtained by freeze/thaw cycles. Wehypothesized that a reorganization of exosomes upon sonication may alterthe content of surface proteins as well as organization of lipidbilayers that resulted in the increased exosomal interactions withcellular membranes of target cells. Obviously, this effect may play apositive role and overpower negative effects of decreased uniformity andincreased visibility of exosomal carriers for the cells of immune systemmentioned above.

Concerning the antioxidant activity, exoCAT formulations showed theefficient ROS deactivation and significant neuroprotective effectsagainst oxidative stress in vitro. In accordance with the loadingefficiency, exoCAT obtained by sonication and extrusion provided themost potent neuroprotection. We reported earlier that exosomes secretedfrom preloaded with nanoformulated catalase macrophages were accumulatedin adjacent cells diffusing broadly throughout the cytoplasm andavoiding degradation in lysosomes (Haney et al., Nanomedicine (Lond)7:815 (2012)). This mechanism enabled the drug to reach differentintracellular compartments, such as mitochondria, and endoplasmicreticulum, and produce potent therapeutic effects (Haney et al.,Nanomedicine (Lond) 7:815 (2012)). We speculated that the same favorableintracellular localization of exoCAT may support the superiorantioxidant and protective activity of exoCAT in neurons.

The intranasal administration provides two main routes for the CNS drugdelivery: a) transport across the single epithelial cell layer directlyto the systemic blood circulation without first-pass hepatic andintestinal metabolism; and b) transport along the olfactory nerve cells,when drug can bypass the BBB and enter the brain directly. Furthermore,this route is attractive due to the possibility of non-invasive multipletreatments with high patient compliancy. Interesting, some investigatorshypothesized that PD have its origin in the bulbs olfactory (Braak etal., Neurobiol. Aging 24:197 (2003)). Subsequently, it could spread,ascending cell-by-cell through brainstem, midbrain, and other regions ofthe brain, and finally result in PD. Therefore, we reasoned thatintranasal administration of exoCAT may work the same way deliveringtherapeutic catalase to the affected brain areas. We report here thatintranasally administered exosomes diffused through the mouse brain,localizing predominantly in the cerebral frontal cortex, central sulcus,and cerebellum.

The most important finding of our investigation is that selected exoCATformulations significantly decreased brain inflammation and increasedneuronal survival in a PD mouse model. The mechanism of these effects isyet to be uncovered. We hypothesized the encapsulation of catalase intoexosomes may preserve catalase enzymatic activity, prolong the bloodcirculation time, reduce immunogenicity, and improve its interactionwith epithelial cells, thus improving drug transport and therapeuticeffects in PD. Here, we investigated two exosomal formulations that wereobtained by saponin treatment, and sonication. These formulations werechosen as the most efficient ones that can provide high loading andsustained drug release. In addition, we evaluated whether thereformation of exosomes upon sonication affected their therapeuticefficacy in vivo. We demonstrated that both formulations significantlydecreased neuroinflammation and provided potent neuroprotection in6-OHDA mouse model. Furthermore, catalase-loaded exosomes obtained bypermeabilization with saponin have superior therapeutic effects thanthose obtained by sonication. It is likely that exoCAT obtained bypermeabilization with saponin might have better uniformity in theirsurface morphology presumably with the intact membrane proteins. Thismay lead to a lower visibility for RES and clearance by macrophages.Overall, successful development of exosome-mediated delivery of catalasecould lead to a viable therapy for patients with PD.

In clinical settings, different approaches may be applied to introduceexosomal-based drug delivery systems. First, exosomal carriers harvestedfrom peripheral blood monocytes by apheresis will be loaded with atherapeutic agent and re-administered back into the patient. As analternative approach, stem cells may be harvested from bone marrow,propagated in culture to obtain specific cell types, or even subtypes,and then released naïve exosomes will be loaded with a therapeuticagent. Although this approach would require a more invasive procedure, asignificant amount as well as storage of well-characterized exosomalcarriers will be possible (Muller et al., Nature Rev. Neurosci. 7:75(2006)). Noteworthy, exosomes can be concentrated, lyophilized, andreconstituted in water solutions, as this study demonstrated. This willallow scalability, standardization, and consistency of manufacturingdifferent lots of exosomal drug formulations, when a considerable amountand long-turn storage of exosomes might be required. Finally, a libraryof various types of exosomal carriers for different drug formulationscould be developed in future and stored in stock for emergencysituations.

Also of note, further tailoring exosomes can provide biologically-activecarriers that may be modified in accordance to the disease and producecytotoxic (for a cancer treatment) or neuroprotective (for the treatmentof neurodegenerative disorders) effects enhancing the therapeuticoutcomes. Thus, drug-loaded exosomes may well serve as a next generationdrug delivery mechanism that combines nanoparticle size withnon-cytotoxic effects, a high drug carrying capacity, and a lowimmunogenic profile.

Conclusion

This work demonstrates that exosomes are exceptionally potent carriersfor therapeutic protein, catalase. We developed an efficient method ofthe drug loading into exosomes without significantly altering theirstructure, and showed that exosomes loaded with catalase efficientlyaccumulate in neurons and microglial cells in the brain and produce apotent neuroprotective effect. These findings indicate that an exosomalbased formulations could be a valuable tool in the future for thetherapy of neurodegenerative disorders. Of course, the complexity ofthese interventions is challenging, yet they promise an unparalleledefficacy in the treatment of many life-threatening conditions, includingthose lacking effective pharmacotherapy. Moreover, a positive outcomewould also suggest the more general applicability of this innovativeapproach for delivering therapeutics to the central nervous system (CNS)and beyond.

Example 2 Development of Exosome-Encapsulated Drugs to Treat MultidrugResistant (MDR) Cancer

In this example, anti-cancer drugs, paclitaxel (PTX) and doxorubicin(DOX), are loaded in exosomes, and the obtained exosome-based drugformulations are used for delivery of these drugs to cancer cells.Superior activity of exosome-based drug formulations against MDR cancercompared to commercial drug formulation has been demonstrated. Theexosomes are shown to deliver the incorporated drug to pulmonarymetastasis and display superior anti-cancer activity against metastaticcancer in a live organism.

Methods

Reagents: PTX and DOX was purchased from LC Laboratories (Woburn,Mass.). Lipophilic fluorescent dyes,1,1′-dioctadecyl-3,3,3′,3′-tetramethylindo-carbocyanine perchlorate(DIL), and2-decanoyl-1-(0-(11-(4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-propionyl-amino)undecyl)-sn-glycero-3-phosphocholine(BODIPY-PC), were purchased from Invitrogen (Carlsbad, Calif.) andMolecular Probes (Eugene, Oreg.), respectively. Rhodamine 123 (R123),4′,6-diamidino-2-phenylindole dihydrochloride (DAPI), and Triton X-100were obtained from Sigma-Aldrich (St. Louis, Mo.). Cell culture mediumand fetal bovine serum (FBS) were purchased from Gibco LifeTechnologies, (Grand Island, N.Y.). Fluorescent polystyrenenanoparticles (Fluoro-Max G100) were obtained from Thermo FisherScientific (Waltham, Mass.). ExoQuick-TC™ Exosome Precipitation Solutionwas obtained from System Biosciences (Mountain View, Calif.).

Cells: RAW 264.7 macrophages, Madin-Darby canine kidney MDCK_(WT) andMDCK_(MDR1) cells were purchased from ATCC (Manassas, Va.) and culturedin Dulbecco's modified Eagle's medium (DMEM) high glucose (Gibco)supplemented with 10% FBS, 1% penicillin and streptomycin at 37° C. and5% CO₂. Murine Lewis lung carcinoma cell subline (3LL-M27), a highlymetastatic lung clone, was a generous gift from Dr. L. Pelletier (CHUL,Laval University, QC, Canada). Pgp protein levels in sensitive andresistant cancer cells were determined by western blot as previouslyreported (Batrakova et al., Br. J. Cancer. 85:1987 (2001)) usingmonoclonal antibodies to Pgp, C219 (Dako Corp., Carpinteria, Calif.; atdilution 1:100), and secondary horseradish peroxide donkey anti-mouseIgG antibodies (Amersham Life Sciences, Cleveland, Ohio; at dilution1:1500). To correct for loading differences, the Pgp levels werenormalized to the constitutively expressed β-actin stained withanti-β-1-chicken integrin (Sigma Chemical Co., at dilution 1:200).Specific bands were visualized using a chemiluminescence kit (Pierce,Rockford, Ill.).

Characterization of Exosomes: Exosomes were harvested from theconditioned media of RAW 264.7 cells cultured in exosome-depleted mediausing the ExoQuick-TC™ Kit (System BioSciences; Mountain View, Calif.)and characterized by NTA, DLS, AFM and Western Blot Analysis asdescribed previously (Haney et al., J. Control. Release (2015) Epub2015/04/04). BODIPY-PC was used as a probe to examine the fluidicproperties of exosomal membranes as described earlier (Laulagnier etal., Blood Cells Mol. Dis. 35:116 (2005) Epub 2005/07/19). Briefly, 30μL exosomes with a concentration of 4×10¹¹ particles/mL were mixed with20 μL BODIPY-PC (0.03 mg/ml) (Boldytev et al., Bioorganicheskaia khimiia32:87 (2006) Epub 2006/03/10) (31) and supplemented with 70 μL deionizedwater; the mixture was incubated for 45 min at 37° C. in the dark.Unbound label was removed using a Zeba™ column (Life Technologies).

Drug Loading into Exosomes: For PTX and DOX loading into exosomes,purified exosomes (˜10¹¹ exosomes) were first mixed with PTX or DOX in 1mL PBS. Different methods of drug loading were investigated: incubationat room temperature (RT), electroporation, and sonication. For theincubation method the admixture was incubated at 37° C. for 1 hour withshaking. For the electroporation method, exosomes were mixed with PTXand added to a chilled 4 mm electroporation cuvette. The mixture wasthen electroporated using an Eppendorf Eporator (Eppendorf AG, Hamburg,Germany) at 1000 kV for 5 ms, and then incubated at 37° C. for 30 min toallow for recovery of the exosomal membrane. For the sonication methodthe PTX-exosome or DOX-exosome mixture was sonicated using a Model 505Sonic Dismembrator with 0.25″ tip with the following settings: 20%amplitude, 6 cycles of 30 s on/off for three minutes with a two minutecooling period between each cycle. After sonication, exoPTX or exoDOXsolution were incubated at 37° C. for 60 min to allow for recovery ofthe exosomal membrane. Excess free drug was separated from exoPTX orexoDOX by size exclusion chromatography using a NAP-10 Sephadex G25column (GE Healthcare, Buckinghamshire, UK).

The amount of PTX loaded into exosomes was measured by a highperformance liquid chromatography (HPLC) method. Briefly, exoPTX (10¹⁰exosomes/0.1 mL) in a microcentrifuge tube was placed on a heating blockset to 75° C. to evaporate solvent. Then, an equal volume ofacetonitrile was added and the mixture was vortexed, sonicated and thencentrifuged at 13,000 rpm (Thermo Legend Micro 21) for 10 min. Followingcentrifugation, the supernatant was taken and filtered through a CorningRegenerated Cellulose 0.2 μm syringe filter and transferred into HPLCautosampler vials. 20 μL aliquots were injected into the HPLC system(Agilent 1200, Agilent Technologies, Palo Alto, Calif.). All analyseswere performed using a C18 column (Supelco Nucleosil C18, 250 mm×4.6 mm,5 μm, 100 Å, Sigma-Aldrich) with a mobile phase of H₂O:acetonitrile(45:55, v/v) at a flow rate of 1 mL/min at 30° C. Absorbance wasmeasured at 227 nm to monitor the elution of PTX.

To measure PTX release, freshly prepared exoPTX were placed in a 300KMWCO Float-A-Lyzer G2 device (Spectrum Laboratories, Houston, Tex.). Thedevice was then placed in PBS under sink conditions at RT with stirring.Samples were taken at time points from inside the dialysis tube and wereanalyzed by HPLC as described above. The amount of PTX released fromexoPTX was expressed as a percentage of total PTX and plotted as afunction of time.

Accumulation of Exosomes and Exosome-incorporated PTX in Cancer Cells:To quantify the amount of exosomes taken up by cells, exosomes werestained with a lipophilic fluorescent dye, DIL as described previously(Haney et al., J. Control. Release (2015) Epub 2015/04/04). Then,DIL-labeled exosomes, or fluorescently-labeled liposomes, or polystyrenenanoparticles (NPs, Fluoro-Max G100, Thermo Fisher Scientific), wereadded in equal numbers (˜10⁸ particles/well) and incubated with 3LL-M27cells at 37° C. and 5% CO₂ for various times. After each time point, themedia was removed and cells were washed 3× with PBS and fixed byincubating with Formal-Fixx (Thermo Fisher Scientific), and examined byconfocal microscopy or using a Shimadzu RF5000 fluorescentspectrophotometer. In case of exoPTX or Taxol, drugs were added inequimolar amounts to the MDCK_(WT), or MDCK_(MDR1) cells and incubatedfor 72h. The cell suspension was then lysed and analyzed for PTX contentby HPLC as described above.

In vitro Cytotoxicity Assay: The in vitro antitumor efficacy of exoPTXwas assessed using a standard MTT(3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazoliumbromide) assaywith three cancer cell lines, and compared to Taxol as described earlier(Batrakova et al., J. Control. Release 143:290 (2010) Epub 2010/01/16).Briefly, cancer cells (MDCKMDR1, MDCKwt, and 3LL-M27) were seeded at5,000 cells/well in 100 μL of media in 96-well plates overnight. Variousconcentrations of exosomes isolated from macrophages conditioned mediaand loaded with PTX by sonication, or empty sonicated exosomes, orTaxol, or PTX were added to cancer cells for 48 hours at 37° C., 5% CO₂.Following the incubation, the cells were washed and incubated with MTTreagent as described in Batrakova et al., Mol. Pharm. 3:113 (2006) Epub2006/04/04. The cytotoxic activity of PTX was then evaluated using astandard MTT assay (Ferrari et al., J. Immunol. Meth. 131:165 (1990)).The absorbance at 570 nm was measured using a Shimadzu RF5000fluorescent spectrophotometer. The survival values were determined inrelation to control cells cultured in drug-free media. All experimentswere repeated at least three times. SEM values were less than 10%.

Production of a Lentiviral Vector (LV) and Transduction of Lewis lungcarcinoma (LLC) cells: Lentiviral vector encoding a fusion between theoptical reporter mCherry (GBM8FlmC, red) and firefly luciferase (FLuc)were created by PCR amplification of the cDNA sequences for mCherry andFLuc from pEmCherry (Clontech) and pcDNA-Luciferase (Addgene) withrestriction enzyme sequences that were engineered into the primers. Tocreate the final constructs, mCherry was digested with BamHI/EcoV andFLuc was digested with EcoV/XhoI. The digested fragments were ligatedinto the BamHI/XhoI digested pTK402 LV transfer vector (a kind gift fromDr. Tal Kafri, The University of North Carolina at Chapel Hill).LV-mCherryFLuc viral vectors were packaged in 3LL-M27 cells by transienttransfection using the psPAX2 and pMD2.G (Addgene) packaging plasmidsand following previously described protocols (Sena-Esteves et al., J.Virol. Meth. 122:131 (2004) Epub 2004/11/16).

To utilize bioluminescence and fluorescence imaging, 3LL-M27 cells weretransduced with lentiviral vectors encoding an mCherry and Renillaluciferase (mC-RL) fusion protein. The viral construct also encoded fora puromycin resistance gene downstream of mCherry which was introducedto enable for selection of nearly 100% positively transduced cells. Arobust expression of both the fluorescent and bioluminescent markers wasobserved, and no difference in proliferation was detected betweenmodified and unmodified cells. These cells (8FlmC-FLuc-3LL-M27) wereused for biodistribution and therapeutic efficacy studies.

Biodistribution of Exosomes in Mice with Pulmonary Metastases: Theexperiments were performed with female C57BL/6 mice (Charles RiverLaboratories, Durham, N.C.) eight weeks of age in strict accordance withthe recommendations in the Guide for the Care and Use of LaboratoryAnimals of the National Institutes of Health. The animals were kept fiveper cage with an air filter cover under light- (12-hours light/darkcycle) and in a temperature-controlled (22±1° C.) environment. Allmanipulations with the animals were performed under a sterilized laminarhood. Food and water were given ad libitum.

C57BL/16 mice (n=4) were injected intra tail vein (i.v.) with8FlmC-FLuc-3LL-M27 cells (5×10⁶ cells/mouse in 100 μL saline) and tumorlung metastases were allowed to establish for 10-12 days. Twelve daysfollowing cancer cells i.v. injection, DID-labeled exosomes isolatedfrom autologous macrophages were administered intranasally (i.n., 10⁷particles/10 μl×2) to mice with lung metastases. Four hours later, micewere sacrificed, perfused, lungs were extracted and sectioned on amicrotome at a thickness of 20 μm; nuclei were stained with DAPI (300mM, 5 min). The images of lung sections were examined by a confocalfluorescence microscopic system ACAS-570 and corresponding filter set,and processed using ImageJ software.

In another experiment, mice with established GBM8FlmC-metastases wereinjected i.n. with non-labeled exosomes loaded with DOX by sonication asdescribed above (10⁷ particles/10 μL×2). Four hours later mice weresacrificed, perfused; lungs were extracted, sectioned, andco-localization of DOX with pulmonary metastases was visualized byconfocal microscopy.

Therapeutic Efficacy of exoPTX against Pulmonary Metastases: Theantineoplastic effects of exoPTX were evaluated in a mouse model ofpulmonary metastases. For this purpose, C57BL/6 mice were i.v. injectedwith 8FlmC-FLuc-3LL-M27 cancer cells (5×10⁶ cells/100 μL/mouse). Fortyeight hours later, mice were treated i.n. with exoPTX (10⁷ particles/10μl×2), or Taxol (50 mg/kg/mouse), or saline as a control (n=7) everyother day with a total of seven treatments. Tumor progression wasmonitored by luminescence using the IVIS system as described inBrynskikh et al. (Nanomedicine (Lond). 5:379 (2010) Epub 2010/04/17).The animals were imaged at various time points (1-22 days)post-treatment as described (Brynskikh et al., Nanomedicine (Lond).5:379 (2010) Epub 2010/04/17). The chemoluminescent signal wasquantified by Living Image® 2.50 software. To assess the amount ofcancer metastases at day 22, mice were sacrificed, perfused, and lungslides obtained on microtome (Thermo Scientific) were examined byconfocal microscopy.

Statistical Analysis: For the all experiments, data are presented as themean±S.E.M. Tests for significant differences between the groups wereperformed using a t-test or one-way ANOVA with multiple comparisons(Fisher's pairwise comparisons) using GraphPad Prism 5.0 (GraphPadsoftware, San Diego, Calif.). A minimum p value of 0.05 was chosen asthe significance level.

Results

Manufacture and characterization of exosomal formulations of PTX(exoPTX): Exosomes collected from the conditioned media of RAW 264.7macrophages were characterized by size, charge, protein content, andmorphology (FIGS. 12A, 12B, and 12D). Exosomes showed elevatedexpression of exosome-associated proteins (Alix, TSG101, and Flotillin)as compared to cell lysate, which displayed greater levels of β-actin(FIG. 12B). Naïve empty exosomes had a narrow size distribution, with anaverage particle diameter of 110.4±4.2 nm and 70.8±2.8 nm as revealed byNTA and DLS, respectively (FIG. 12A); and a round morphology as shown byAFM imaging (FIG. 12D).

PTX was incorporated into exosomes using three methods: a) incubation atroom temperature (RT), b) electroporation, and c) mild sonication. Theobtained exoPTX formulations were purified from the non-incorporateddrug by size-exclusion chromatography and analyzed by HPLC to determinethe loading capacity (LC). The typical HPLC profiles for PTX extractedfrom exosomes (B) and PTX standards (A) are shown on FIG. 13 . Theamount of PTX loaded into exosomes increased as follows: incubation atRT<electroporation <<sonication (FIG. 12A). Interestingly, DLS studiesrevealed that the size of exoPTX nanoformulations increased similarly,with the smaller being exoPTX nanoparticles obtained by electroporationor incubation at RT, and the larger being exosomes loaded with PTX bysonication (FIG. 12A). These data were confirmed by NTA analysis.Exosomes sonicated in the absence of PTX were even larger than thosesonicated with PTX (FIG. 12A). We hypothesized this may be due to thestabilization of exosomal membranes by the incorporated drug. Wesuggested that a reorganization of exosomal membranes under sonicationmay enable PTX diffusion across relatively tight lipid bilayers. Indeed,fluorescence polarization measurements revealed significant decreases(more than two times) in membrane microviscosity upon sonication (FIG.12C). To address a concern about possible loosing of exosome-boundproteins, we examined the levels of Alix, TSG101, and Flotillin inexosomes before and after sonication using western blot technique (FIG.12B). The data indicate that the mild sonication utilized for PTXloading with six cycles, and intermediate time out for cooling down andrestoration, did not significantly affect the protein content ofexosomes. It is known that the anionic phospholipid phosphatidylserineis abundant on cell membranes and contributes to the surface charge ofindividual cellular membranes. To this end, all loading procedures didnot significantly alter the zeta potential of the nanocarriers (FIG.12A), suggesting that there were also no major alterations of the lipidcontent of exosomal membranes. Finally, a complete restoration ofmembrane microviscosity was observed after a one hour incubation at 37°C. following sonication procedure (FIG. 12C). Retention of shape andround morphology of exosomes (FIG. 12D) confirmed this hypothesis.

Next, exoPTX showed burst release within the first three hours, and thendisplayed a sustained release profile thereafter (FIG. 12E). The highstability of exosomes in an aqueous solution was demonstrated at threetemperatures: 4° C., RT, and 37° C. over a period of one month (FIG. 14). Overall, the mild sonication procedure provided the highest amount ofdrug loading; the obtained LC of 28.29 f 1.38% (FIG. 12A) was muchhigher than the LC of commercially available formulations of PTX, Taxol(˜1% LC), or Abraxane (˜10% LC). Therefore, exoPTX obtained bysonication was selected for further experiments.

Accumulation and therapeutic efficacy of exoPTX in target cancer cellsin vitro: The ability to deliver the drug payload into target cells wasstudied with fluorescently-labeled exosomes in 3LL-M27 cells, andcompared to the commonly used nanocarriers, liposomes and polystyrenenanoparticles (NPs) (De Jong et al., Int. J. Nanomedicine. 3:133 (2008)Epub 2008/08/09) with the same size and level of fluorescence (FIGS.15A-15B). Liposomes were prepared by a reverse phase evaporation methodas described previously (Haney et al., J. Control. Release (2015) Epub2015/04/04). Confocal images revealed a profound accumulation ofexosomes in cancer cells and limited uptake of liposomes and NPs (FIG.15A). This result was further confirmed and quantitated in accumulationstudies (FIG. 15B). Exosomes were taken up about 30 times better thanthe synthetic nanoparticles, suggesting that PTX loaded into exosomescan be efficiently delivered to cancer cells in therapeuticallysufficient quantities. These results clearly show the advantages ofexosome-based drug delivery systems over common synthetic nanocarriersand confirmed our previous report regarding the profound accumulation ofexosomes in neuronal PC12 cells (Haney et al., J. Control. Release(2015) Epub 2015/04/04).

The anticancer effects of exoPTX were evaluated in a resistant MDR cellsexpressing the drug efflux transporter, Pgp (MDCK_(MDR1)), and theirsensitive counterparts (MDCK_(WT)). The loading of PTX into exosomessignificantly increased drug cytotoxicity as compared to PTX alone, orTaxol in both sensitive MDCK_(WT) and resistant MDCK_(MDR1) cancer cells(Table 2). These results are consistent with earlier reports regardingincreased cytotoxicity of another anticancer agent, DOX in cancer cells(Tian et al., Biomaterials 35:2383 (2014) Epub 2013/12/19). The mostintriguing observation was made, when the effects of various PTXformulations were compared in sensitive and resistant cancer cells. Forthis purpose, the increased cytotoxicity of the drug was expressed inthe form of a “Resistance Reversion Index” (RRI), i.e. ratio of IC₅₀ ofPTX alone, and in nanoformulation (e.g. IC_(50,PTX)/IC_(50,exoPTX), orIC_(50,PTX)/IC_(50,taxol)). Both PTX formulations caused significantsensitization of MDR cells with respect to PTX (Table 2). In particular,RRI for exoPTX in MDCK_(MDR1) and MDCK_(WT) was 53.33 and 18.38,respectively. In contrast, RRI for Taxol in both resistant and sensitivecancer cells was c.a. 6 (Table 2). Noteworthy, empty sonicated exosomesdid not show any cytotoxicity in all studied cell lines (FIG. 16 ).Thus, the increase in PTX cytotoxicity afforded by exoPTX was greater inPgp-overexpressing cells than their sensitive counterparts (Table 2).

TABLE 2 Drug Cell line IC50 (ng/mL) RRI exoPTX 3LL-M27 13.57 ± 1.33 9.32MDCK wt 23.33 ± 3.77 18.38 MDCK MDR1  187.5 ± 38.65 >53.33 Taxol 3LL-M2723.16 ± 1.88 5.46 MDCK wt 69.54 ± 11.5 6.17 MDCK MDR1 1708.67 ±299.93 >5.85 PTX 3LL-M27 126.41 ± 31.31 1 MDCK wt 428.77 ± 63.37 1 MDCKMDR1 >10,000 1

Mechanistic studies of exoPTX cytotoxic effects: We hypothesized thatexoPTX may alter drug intracellular trafficking and bypass the drugefflux system more efficiently than Taxol (in particular, exoPTX mayfacilitate endosomal release of PTX from exosomes in cancer cells). Toprove this hypothesis, we examined the accumulation levels of afluorescent probe and Pgp substrate, DOX, incorporated into exosomes(exoDOX) in MDCK_(MDR1) and MDCK_(WT) cells. First, elevated Pgpexpression levels in MDCK_(MDR1) cells, and low, if any, Pgp levels inMDCK_(WT) cells were confirmed by western blot (FIG. 17A). Next, theuptake of free DOX and exosome-incorporated drug, exoDOX, was comparedin the presence/absence of a Pgp inhibitor, verapamil. As expected, theincorporation of Dox into exosomes significantly increased drugaccumulation levels in both sensitive and resistant cancer cells (FIG.17B). Inhibition of Pgp-mediated drug efflux by verapamil increasedaccumulation of free DOX in resistant MDCK_(MDR1) cells, but did notalter drug accumulation in their sensitive counterparts. Remarkably,verapamil treatment did not affect exoDOX accumulation in resistantMDCK_(MDR1) cells, indicating that drug incorporation into exosomesallowed it to bypass this resistance mechanism (FIG. 17B).

We demonstrated earlier that the incorporation of Pgp substrates, suchas R123 or DOX, into block-copolymer-based nanocarriers, i.e. Pluronic®micelles, increased drug accumulation in resistant cancer cells due tothe inhibition of Pgp efflux transporter by Pluronic® macromoleculesincorporated into the membranes of resistant cancer cells (Batrakova etal., Br. J. Cancer 85:1987 (2001); Batrakova et al., Pharm. Res. 16:1373(1999); Batrakova et al., J. Pharmacol. Exp. Ther. 304:845 (2003);Batrakova et al., Pharm. Res. 20:1581 (2003)). To exclude thepossibility that exosomes may inhibit Pgp-mediated efflux by theirfusion with cellular membranes, accumulation of R123 in both resistantand sensitive MDCK cancer cells was assessed. R123 does not incorporateinto exosomes upon incubation at RT, as was confirmed in our preliminarystudies (FIG. 18 ). For this purpose, MDCK_(WT) and MDCK_(MDR1) cellmonolayers were pretreated with a Pgp inhibitor, verapamil (positivecontrol), or empty exosomes, or media (negative control), and then weretreated with R123 solutions for two hours (FIGS. 19A-19B). R123accumulation levels in resistant MDCK_(MDR1) cells were increased almostfive times in verapamil pre-treated cells. In contrast, treatment withempty exosomes did not affect R123 accumulation in MDCK_(MDR1) cells(FIGS. 19A-19B). As expected, neither treatment with verapamil, nor withempty exosomes, altered R123 accumulation levels in sensitive MDCK_(WT)cells. This indicates that exosomes themselves do not appear to have anyinhibitory effect on Pgp-mediated efflux; they allow incorporated drugsto bypass the Pgp efflux protein perhaps, through endocytosis-mediatedtransport and/or fusion with plasma membranes.

Co-localization of Airway-delivered Exosomes with Pulmonary Metastasesin LLC mouse model: To establish an in vivo model of pulmonarymetastases, C57BL/6 mice were injected intra-tail vein (5×10⁶ cells/100μL) with 3LL-M27 cells. Important, this model is particularly relevantto the present investigation, as it was demonstrated that 3LL-M27 tumorcells have high expression levels of the MDR1 gene and Pgp expression invivo (Batrakova et al., J. Control. Release. 143:290 (2010) Epub2010/01/16). Twenty days later, mice were sacrificed, perfused, andlungs were isolated, sectioned, and stained with Hematoxylin and Eosin(H&E). Multiple metastases were detected in whole lungs (FIGS. 20A-20C).Histological evaluations revealed that the structure of alveoli intumor-bearing lungs was disrupted by tumor cells (FIG. 20B). Next, micewere injected with 8FlmC-FLuc-3LL-M27 (FIGS. 21A-21B) intra-tail vein asdescribed in Methods section. 22 days later, autologous exosomes stainedwith a fluorescent dye, DiD (green), were i.n. administered to mice withpulmonary metastases. Four hours later, mice were sacrificed, perfused;lungs were sectioned on microtome and examined by confocal microscopy.Nuclei were stained with DAPI (FIGS. 21A-21B). Confocal images revealed97.9±2.0% of exosomes were co-localized with lung metastases (FIGS.21A-21B), indicating efficient targeting of exoPTX in vivo. A similarexperiment was performed with exoDOX formulation in order to visualizedrug delivery to pulmonary metastases. Non-labeled exosomes loaded withDOX were i.n. administered to mice with established 8FlmC-FLuc-3LL-M27metastases. Confocal images revealed a substantial amount of DOX in thelungs co-localized with cancer cells (data not shown). These resultsindicate that airway-administered exosomes reached pulmonary metastasesand delivered their drug payload to target cancer cells.

PTX-loaded exosomes produce strong antineoplastic effect in mice withlung metastases: To provide insight into the potential of exosome-basedtherapeutic delivery, the antineoplastic effects of exoPTX wereevaluated in an LLC mouse model. For this purpose, C57BL/6 mice werei.v. injected with 8FlmC-FLuc-3LL-M27 cells as described above. 48 hourslater, mice were i.n. administered exoPTX (10⁷ particles/10 μl×2), orTaxol, or saline as a control every other day totally, seven times. Theprogression of pulmonary metastases in treated mice was monitored usingIVIS by observing the luminescence of transduced cancer cells in livinganimals (FIG. 22A). Representative images of dorsal planes of theinjected animals at day 22 are shown on (FIG. 22A). A significant(p<0.05) inhibition of metastases growth by exoPTX treatment wasdemonstrated (FIG. 22C). Taxol treatment was shown to inhibit metastasesgrowth as compared to non-treated controls (saline), although to alesser extent than exoPTX treatment. At the end point of the experiment(day 22), the lung sections were visualized using confocal microscopy(FIG. 22B). A marked number of fluorescent transduced cancer cells weredetected in the lungs of animals treated with Taxol (FIG. 22C), whileonly a few cancer cells were observed in the lungs of exoPTX treatedanimals. Noteworthy, sonicated empty exosomes showed no significantinhibition on pulmonary metastases growth (FIG. 22A, 22B). This confirmsthe superior antineoplastic efficacy of exoPTX as compared to Taxol.

Discussion

Exosomal carriers can provide advantages of both cell-based drugdelivery and nanotechnology for efficient drug transport capable ofovercoming various biological barriers. One difficulty is the efficientloading of exosomes with a therapeutic agent without significant changesin the structure and content of exosomal membranes. In the presentstudy, we utilized various methods for PTX incorporation into exosomes:incubation at RT, electroporation, and mild sonication. The mildsonication of exosomes in the presence of PTX provided the greatestloading capacity. PTX, a highly hydrophobic compound is likely to beincorporated into the hydrophobic inner region of the lipid bilayers ofexosomes. We hypothesized that the high rigidity of exosomal membranesmay be decreased upon sonication and would thus allow for PTXincorporation into lipid bilayers resulting in a high loading capacity.This hypothesis was confirmed by significant decreases in microviscosityof exosomal membranes upon sonication. Nevertheless, we do not exclude apossibility that a considerable amount of PTX may also be adhered to thesurface of exosomes that may account for the burst release from exoPTXobserved in the first 3-4 hours. It is worth noting that ˜30% of loadeddrug was still associated with exosomes after one week in an aqueoussolution. Importantly, drug located in the inner bilayer of exosomes mayalso be available for use: as the exosomal membrane fuses with the cellor endosomal membrane, its intraluminal cargo may be released into thecytosol of a target cell. Next, the aggregation stability of exoPTXformulations is imperative for their use in clinic. We report here thatthe obtained exoPTX formulation was stable at various conditions forover a month. In addition, exosomes may be lyophilized andreconstituted, while retaining their morphology and othercharacteristics (Haney et al., J. Control. Release (2015) Epub2015/04/04). This provides a clinical link for exosome-based drugformulations, suggesting that multiple lots of exoPTX may be preparedand stored prior to treatment.

Exosomes possess an extraordinary ability to interact with andaccumulate in target cancer cells. The obtained data indicates exosomesare taken up in considerably greater numbers than liposomes orpolystyrene NPs. In addition, the incorporation of PTX into exosomes maynot only increase its solubility, but also allow for overcoming ofPgp-mediated drug efflux. We demonstrated here that incorporation of aPgp substrate, DOX, into exosomes significantly increased drugaccumulation in MDR cells as compared to free DOX, or even to DOX in thepresence of a Pgp-inhibitor, verapamil. Next, the increase incytotoxicity afforded by the exosomal formulation of PTX wasconsiderably greater in resistant cells (RRI>53.33) than sensitive cells(RRI=18.35), while Taxol showed almost no difference in resistant(RRI>5.85) vs. sensitive cancer cells (RRI=6.17). This effect may beattributed to the difference in route of internalization of exoPTX, ascompared to Taxol. Exosomes and micelles, such as those found in Taxol,are taken up by endocytosis, but exosomes have superior uptake due tothe presence of adhesion proteins, tetraspanins, integrins,immunoglobulins, proteoglycans, and lectins (Mulcahy et al., J.Extracellular Vesicles 3 (2014) Epub 2014/08/22) (42), which are notfound on artificial nanoparticles. Furthermore, exosomes consist ofcellular membranes that may fuse with the plasma and/or endocyticmembranes and deliver their cargo, bypassing Pgp-mediated efflux.Noteworthy, exosomes themselves did not inhibit Pgp, as thepre-treatment with empty exosomes did not increase accumulation of thePgp substrate, R123, in resistant cancer cells.

Interestingly, it was suggested that the MDR efflux transporters arelikely contribute to the production of drug-loaded exosomes during theirbiogenesis in resistant cancer cells (Safaei et al., Mol. Cancer Ther.4:1595 (2005) Epub 2005/10/18). In addition, Pgp may be also involved inthe increased drug sequestration in lysosomes and MVB (Yamagishi et al.,J. Biol. Chem. 288:31761 (2013) Epub 2013/09/26). Thus, Pgp associatedwith the endosomal membrane excretes the internalized drug into theendosomal lumen, where newly formed cancer exosomes are literallyincubated with the drug and become “drug-loaded” before being releasedfrom the cell. The same effect was reported with PTX inPgp-overexpressing bone marrow mesenchymal stromal cells (SR4987)(Pascucci et al., J. Control. Release 192:262 (2014) Epub 2014/08/02).We hypothesized that exoPTX accumulated in the MDR cancer cells maybypass not only efflux by Pgp transporter located on plasma membrane,but also avoid accumulation in lysosomes and MVB of cancer cells, andtherefore, reduce drug elimination and increase its therapeutic efficacyin resistant tumors. The investigations regarding this hypothesis areunderway in our laboratory.

Finally, the therapeutic efficacy of exoPTX formulation againstpulmonary metastases was demonstrated in an LLC mouse model.Intriguingly, airway-delivered exosomes showed near completeco-localization with cancer metastases in this model. The results wereconfirmed by the significant co-localization of DOX incorporated intoexosomes with cancer cells. We speculated that macrophage-releasedexosomes are likely to have specific proteins on their surface, whichmight allow for their preferential accumulation in cancer cells.Furthermore, it is known that exosome-mediated cell-to-cellcommunication is key in the battle between cancer and the immune system(Finn, Ann. Oncol. 23 Suppl8:viii6-9 (2012) Epub 2012/08/29). Thus,Parolini et al. (J. Biol. Chem. 284:34211 (2009) Epub 2009/10/06) showedthat exosome fusion with target cells occurs more efficiently underacidic conditions, implying that exosomes may be taken up preferentiallyby tumors (which have an acidic microenvironment) rather than thesurrounding healthy tissue. Our results show that exoPTX demonstratedsuperior inhibition of pulmonary metastases growth in LLC mouse model.All three mechanisms mentioned here are likely to have significantimpact on exoPTX anticancer activity, i.e.: (i) preferentialaccumulation in cancer cells, (ii) efficient delivery of incorporatedcargo into target cancer cells, and (iii) by-passing Pgp-mediated drugefflux in resistant cancer cells.

Example 3 Macrophage Exosomes as Natural Nanocarriers for NeurotrophinDelivery to Inflamed Brain

In this example exosomes isolated from macrophages and administeredintravenously (i.v.) are shown to cross the BBB. The exosomes isolatedfrom macrophages are loaded with neurotrophin, the brain derivedneurotrophic factor (BDNF). The BDNF loaded exosomes after i.v.administration are shown to increase delivery of the neurotrophic factorto the brain. This delivery is enhanced in the presence of braininflammation, a condition often present in those diseases for whichbrain delivery of the neurotrophic factor beneficial for the therapy orneurodegenerative and neurodevelopmental disorders and stroke.

Methods

Cell Culture. Raw Mϕs (American Type Culture Collection ATCC® TIB-71TM,Rockville, Md.) between passage 1 and 30 were used. The cells were grownin DMEM medium plus 10% FBS and 1% penicillin-streptomycin, andsubcultured by scraping. The conditioned medium for exosome collectionwas DMEM plus 1% penicillin-streptomycin and 10% FBS pre-centrifuged at120 kg for 140 min to remove serum exosomes. hCMEC/D3 cells (a kind giftfrom Dr. Pierre-Olivier Couraud in Cochin Institute, France) betweenpassage 30 and 35 were used. All cell cultureware for hCMEC/D3 cells wascoated with 0.15 mg/ml rat collagen I. The cells were grown in EBM-2endothelial growth basal medium (Lonza) containing 5% FBS, 1%Penicillin-Streptomycin, 1.4 μM hydrocortisone, 5 μg/ml acid ascorbic,100× diluted chemically defined lipid concentrate (Life technologies),10 mM HEPES and 1 ng/ml human basic fibroblast growth factor (Sigma).

Animals. All animal experiments were conducted under the approval of theUniversity of North Carolina Institutional Animal Care and UseCommittee. Six to eight weeks old male CD-1 mice were purchased fromCharles River Laboratories.

Purification of Exosomes. Exosomes were purified by the commonsequential centrifugation method (El-Andaloussi et al., Nature Protocols7:2112 (20012); Thery et al., Current Protocols in CellBiology/editorial board, Juan S. Bonifacino . . . [et al.] 2006, Chapter3, Unit 3 22). Raw Mϕs were grown in 7 T75 flasks to reach 70-80%confluence. Following two phosphate-buffered saline (PBS) washes, thecells were cultured in 10 ml conditioned medium for 2 days. The mediumwas then collected and centrifuged sequentially at 300 g for 15 min,3,000 g for 15 min, 20,000 g for 70 min, and filtered through 0.2 μmmembrane filters to remove cells and large particles. Exosomes werepelleted at 120,000 g for 70 min, washed by PBS to remove proteins,pelleted again, and then resuspended in 1 ml PBS. The exosome suspensionwas filtered through 0.22 μm membrane filters and stored in −80° C. forat most 3 weeks. Each batch of exosomes contained around 65 μg exosomalproteins as determined by microBCA and 3×10¹¹ exosomes as determined byNTA.

Characterization of Exosomes. Exosomes were characterized by DLS forintensity-weighted z-average diameter, PDI and zeta potential, by NTAfor number-weighted diameter and particle concentration, and by TEM formorphology. For DLS, the size was measured in PBS, and thezeta-potential was measured in 10 mM NaCl at 23° C. with a 1730scattering angle using Zetasizer Nano-ZS instrument (Malvern, UK) in atleast triplicates. For NTA, each sample was diluted 500 times in PBS andloaded into Nanosight NS500 (Malvern, UK). Three videos of 60s with asample advance in between were recorded with the minimal expectedparticle size, minimum track length and blur setting all set toautomatic. For TEM, exosomes were adsorbed onto Formvar coated coppergrid (200 mesh), stained with 2% uranyl acetate and characterized usingZeiss TEM 910 Transmission Electron Microscope (Jena, Germany) at 80 kVaccelerating voltage.

Protein Composition and Exosomal Markers. Mϕs and Mϕ exosomes were lysedwith RIPA buffer mixed with proteinase and phosphatase inhibitorcocktail (Thermo Fisher Scientific). Protein composition and exosomalmarkers were detected by standard SDS-PAGE and western blot underreducing condition (El-Andaloussi et al., Nature Protocols 7:2112(20012)).

Cell Viability. Cell viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay.hCMEC/D3 cells were seeded in 96-well plates at 2000 cells/well inculture medium. After overnight incubation, the cells were treated withtest agents in culture medium for time durations indicated in figurelegend, and let grown in fresh culture medium (200 μl) for another 72 h.20 μl of MTT in PBS (5 mg/ml) was added to each well. After 4hincubation at 37° C., the formed formazan precipitate was dissolved in150 μl of DMSO. Absorbance at 570 nm (A) was read on a microplate readerSpectraMax M5 (Molecular devices). Blanks (wells without cells) thataccount for solvent adsorption and controls (wells with cells withouttest agents) for 100% viability were treated similarly. Cell viability(%) was calculated as((A_(treat)−A_(blank)))/((A_(control)−A_(blank))×100%. Data are means±SDof 6 replicate wells.

Flow Cytometry of Cell Uptake. hCMEC/D3 cells were grown in 24-wellplates at 5×10¹¹ cells/well for 4-5 days to reach confluence. Exosomeswere labeled by adding CM-DiI dyes (2 μg/ml, Life Technologies) to themedium before the first 120 kg pelleting step. In the uptake mechanismstudies, the cells were pretreated with endocytosis inhibitors,carbohydrates or EGTA for 0.5 h, and then co-treated with CM-DiI labeledexosomes (0.6×10¹⁰ exosomes/ml) for 4 h. The inhibition of endocytosismarkers uptake was studied similarly. The endocytosis markers used wereAlexa Fluor 488-Transferrin (10 μg/ml, Life technologies) for clathrinmediated endocytosis, Alexa Fluor 488-CTB (5 μg/ml, Life technologies)for caveolae mediated endocytosis, and FITC-Dextran (70 kDa, Sigma) (10mg/ml) for macropinocytosis. The antibody block assays were done byco-incubating exosomes with antibodies or isotope controls at 100 μg/mlfor 4 h. The cells were washed trice by PBS, detached by 0.25%trypsin/EDTA, collected by centrifugation at 100 g for 10 min, fixedwith 4% paraformaldehyde for 10 min, and then resuspended in 0.35 mlPBS. Viable singlets were gated based on forward scatter and sidescatter. 5,000-10,000 viable singlets were recorded for each sample onBecton Dickinson LSRII (BD Biosciences) using 488 nm and 532 nm lasers.Unless otherwise noted in figure legend, data are not normalized andreported as mean fluorescence±SD of 3 replicate wells.

LSCM. hCMEC/D3 cells were cultured in 35 mm glass bottom dishes (MatTek)at 1×10⁵ cells/well for 5-6 days to reach confluence. In endocytosispathway studies, the cells were treated with CM-DiI labeled exosomes(1×10¹¹ exosomes/ml) and Alexa Fluor 488-Transferrin (25 μg/ml) or AlexaFluor 488-CTB (5 μg/ml) for 0.5 h, and then fixed before imaging. In theimmunofluorescence studies, the cells were treated with CM-DiI labeledexosomes (1×10¹¹ exosomes/ml) for 0.5 h, fixed by 4% paraformaldehyde,blocked with 10% goat serum/0.3% Triton® X-100 in PBS at roomtemperature for 1 h, and incubated with anti-clathrin heavy chain oranti-caveolin 1 antibodies (R&D systems) in 1% goat serum/1% BSA/0.3%Triton® X-100 in PBS at 4° C. overnight. Followed three washes using0.1% BSA in PBS, the cells were incubated with Alexa Fluor 488conjugated secondary antibodies, washed trice and mounted in SlowFade®Gold antifade mountant (Life technologies). Images were collected byZeiss CLSM 700/710 spectral confocal laser scanning microscope (Jena).Mander's colocalization coefficients were calculated using Image J andJACoP plugin (Schneider et al., Nature Methods 9:671 (2012); Bolte etal., J. Microsc.-Oxford 224:213 (2006)).

Iodine Labeling. Exosomes and proteins were labeled with iodine bychloramine-T method (Yi et al., J. Controlled Release 191:34 (2014)).Briefly, exosomes or proteins were mixed with 1 mCi of Na¹²⁵I or Na¹³¹I(Perkin Elmer) and 10 μg of chloramine-T in phosphate buffer (0.25 M, pH7.5) for 60 s. Labeled exosomes and proteins were purified by IllustraNap-5 columns (Life technologies) and collected in tubes pretreated with1% BSA in PBS to prevent nonspecific adsorption. The iodine association(iodine in labeled sample/total iodine) was determined bytrichloroacetic acid precipitation method (Yi et al., J. ControlledRelease 191:34 (2014)). Briefly, 1 μl of purified samples was mixed with0.5 ml of 1% BSA in PBS and 0.5 ml of 30% TCA, and then centrifuged at5400 g for 10 min. The resulting pellet and supernatant were counted onr-counter (PerkinElmer). The iodine association was calculated as thepercentage of pellet radioactivity to total radioactivity. The iodineassociation for exosomes and BSA/BDNF was higher than 85% and 98%,respectively.

Animal Procedure. Mice were anesthetized with 40% urethane (4 g/kg) byintraperitoneal injection. Iodine labeled substances (4×10⁵ cpm) wereinjected to the right jugular vein. At each time point, blood wascollected from the left carotid artery, allowed to clot and thencentrifuged at 5400 g for 10 min to collect serum. The whole brain andperipheral organs were removed and weighed immediately after bloodsampling. The radioactivity of serum and tissues were counted andnormalized to injected dose (ID) by volume (ml) or weight (g) (% ID/mlor % ID/g). An injection check representing ID was also counted (n=3).

PK data analysis. The noncompartmental PK parameters Vss (ml), Cl(ml/min), MRT_(last) and MRT_(inf) (h) were estimated using Phoenix®WinNonlin® 6.3 (Pharsight). The Ki (slope) and Vi (y-intercept) werecalculated from the linear portion of multiple-time regression analysis(Price et al., J. Pharmacol. Exper. Ther. 333:253 (2010); Patlak et al.,J. Cerebral Blood Flow Metab. 3:1 (1983); Patlak et al., J. CerebralBlood Flow Metab. 5:584 (1985)). Brain/serum ratio (Am/Cp_(t), ml/g) ofco-injected BSA was used to correct for the vascular space or leakage(Banks et al, Brain Behav. Immun. 2010, 24:102 (2010)), and subtractedfrom that of tested substance to get the delta brain/serum ratio. Thedelta brain/serum ratio was plotted against exposure time followingequation

Am/Cp_(t) = Ki^(∫₀^(t)Cp_(t)dt/Cp_(t)) + Vi,

where the exposure time

(∫₀^(t)Cp_(t)dt/Cp_(t))

was the trapezoidal integral of serum cpm at time t (Cp_(t)) from time 0to time t divided by Cp_(t).

Statistical analysis. Statistical analysis was performed using Prism 6.0(GraphPad Software Inc.) unpaired two-tailed student t-test (#p<0.05,##p<0.01, and ###p<0.001), or one-way ANOVA with post Newman-Keulsmultiple comparison test (* p<0.05, ** p<0.01, and *** p<0.001) asindicated in the figure legend.

Abbreviations. Alix, apoptosis-linked-gene-2 interacting protein X; BBB,blood-brain barriers; BDNF, brain derived neurotrophic factor; CTB,cholera toxin subunit B; hCMEC/D3 cells, immortalized human cerebralmicrovascular endothelial cells; ICAM-1, intercellular adhesion molecule1; LAMP 2, lysosome-associated membrane protein 2; LFA-1, lymphocytefunction-associated antigen 1; LPS, lipopolysaccharide; MPS, mononuclearphagocyte system; PK, pharmacokinetics; Raw Mϕ, raw 264.7 macrophages;Tsg 101, tumor susceptibility gene 101 protein.

Results and Discussion

Mϕ exosome is a natural nanomaterial. Exosomes secreted by RAW Mϕs werepurified by the sequential centrifugation method (El-Andaloussi et al.,Nature Protocols 7:2112 (20012); Thery et al., Curr. Protocols CellBiol. 2006, Chapter 3, Unit 3 22). We characterized their sizedistribution and zeta potential by DLS and NTA, morphology bytransmission electron microscopy (TEM), and protein composition bysodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) andwestern blot (FIGS. 23A-23E). Consistent with published results(El-Andaloussi et al., Nature Protocols 7:2112 (20012); Singh et al., J.Immunol. 189:777 (2012)), Mϕ exosomes were a heterogeneous populationwith intensity-weighted z-average diameter of 149 nm, relatively smallpolydispersity index (PDI) of 0.134 as determined by DLS, andnumber-weighted mean diameter of 130 nm, mode diameter of 90 nm by NTA.Using instrument software, the intensity-weighted distribution wasconverted to volume- and number-weighted distributions (FIGS. 24A-24B).The peaks of volume- and number-weighted distributions shifted toslightly smaller diameters. Mϕ exosomes were negatively charged (zetapotential −18 mV) in 10 mM NaCl. TEM showed spherical morphology aspublished (Thery et al., Curr. Protocols Cell Biol. 2006, Chapter 3,Unit 3 22). Occasionally we observed cup-shape as an artifact of sampledrying (Thery et al., Curr. Protocols Cell Biol. 2006, Chapter 3, Unit 322), and aggregation in vitro. Based on SDS-PAGE, the proteincomposition of exosomes differed from their parent Mϕs and fetal bovineserum (FBS) as published previously (Thery et al., Curr. Protocols CellBiol. 2006, Chapter 3, Unit 3 22). Specifically, as further revealedusing western blot, exosomes compared to Mϕs were enriched withapoptosis-linked-gene-2 interacting protein X (Alix) and tumorsusceptibility gene 101 protein (Tsg 101), two exosomal markers relatedto the biogenesis of multivesicular bodies (Urbanelli et al., Genes4:152 (2013)). We also detected in the lysate of Mϕ exosomes twoconserved proteins that are frequently detected in exosomes: atransmembrane protein lysosome-associated membrane protein 2 (LAMP 2)and a cytosolic protein β-actin (Fais et al., Biol. Chem. 394:1 (2013);El-Andaloussi et al., Nature Protocols 7:2112 (20012); Li et al., NatureImmunol. 14:793 (2013); Graner et al., FASEB J. 23:1541 (2009)).

Uptake of Mϕ exosomes in human cerebral microvascular endothelial cells.We further characterized the interactions of Mϕ exosomes with hCMEC/D3cells as an in vitro BBB model (FIGS. 25A-25D). The MTT assay showedthat the viability of these cells was not affected by their exposure toMϕ exosomes for 24 h up to the highest tested exosome concentration of2×10¹¹ exosomes/ml (FIG. 25A). All following studies involving cellsused lower concentrations of exosomes. We labeled exosomes with alipophilic dye CM-DiI to monitor their uptake in cells. The time courseof cellular uptake revealed that after an initial lag period of 4 h, theamount of Mϕ exosomes in hCMEC/D3 cells nearly linearly increased over48 h (FIG. 25B). The concentration dependence of the uptake (at 4 h timepoint) suggested saturation at high concentration of Mϕ exosomes (FIG.25C), similar to the reported uptake of glioblastoma exosomes inglioblastoma cells (Christianson et al., Proc. Natl. Acad. Sci. USA110:17380 (2013)). Non-labeled exosomes blocked uptake of fluorescentlylabeled exosomes in a concentration-dependent manner, supporting thesaturable nature of the uptake of Mϕ exosomes in hCMEC/D3 cells (FIG.25D). This implied a possible receptor-mediated uptake mechanism thatwas confirmed below.

Endocytosis pathways of Mϕ exosomes in hCMEC/D3 cells. The saturableuptake of Mϕ exosomes in hCMEC/D3 cells indicates that these cellsinternalize Mϕ exosomes by some form of receptor-mediated endocytosis,rather than solely by passive fusion or macropinocytosis. Incubation at4° C. completely blocked the uptake of Mϕ exosomes (FIG. 26A),suggesting that their internalization in hCMEC/D3 cells is anenergy-dependent process (Morelli et al., Blood 104:3257 (2004);Escrevente et al., BMC Cancer 11:108 (2011); Tian et al., J. CellBiochem. 111:488 (2010)). To study the endocytosis pathways, wepre-incubated hCMEC/D3 cells with endocytosis inhibitors for 0.5 h, andthen co-incubated with fresh inhibitors and Mϕ exosomes for another 4 h.We selected sucrose (Chen et al., J. Cell Sci. 122:1863 (2009)),nystatin (Chen et al., J. Cell Sci. 122:1863 (2009); Hussain et al., J.Biol. Chem. 286:309 (2011)), and 5-(N-Ethyl-N-isopropyl) amiloride(EIPA) (Feng et al., Traffic 11:675 (2010); Commisso et al., Nature497:633 (2013)) as the inhibitors for clathrin-mediated endocytosis,caveolae-mediated endocytosis and macropinocytosis, respectively. Eachinhibitor diminished uptake of a respective endocytosis marker atnon-toxic concentrations (FIGS. 26A-26D, 27 ): sucrose of transferrin,nystatin of cholera toxin subunit B (CTB), and EIPA of dextran (70 kDa).Each of these inhibitors significantly decreased the uptake of Mϕexosomes, suggesting that exosomes utilized multiple pathways to enterthe cells, similar to the endocytosis of exosomes derived from tumor orimmune cells into respective parent cells (Christianson et al., Proc.Natl. Acad. Sci. USA 110:17380 (2013); Morelli et al., Blood 104:3257(2004); Escrevente et al., BMC Cancer 11:108 (2011); Tian et al., J.Cell Biochem. 111:488 (2010); Feng et al., Traffic 11:675 (2010); Tianet al., J. Cell. Physiol. 228:1487 (2013); Mulcahy et al., J.Extracellular Vesicles 3:doi: 10.3402/jev.v3.24641 (2014)). Moreover, Mϕexosomes colocalized with transferrin, anti-clathrin heavy chainantibodies, CTB and anti-caveolin 1 antibodies at 0.5 h, supporting thatboth clathrin and caveolae mediated the uptake of Mϕ exosomes inhCMEC/D3 cells (FIGS. 28A-28B).

ICAM-1/LFA-1 mediated uptake of Mϕ exosomes in hCMEC/D3 cells. Weanticipated that Mϕ exosomes might interact with BBB using similarmechanisms as Mϕs, from which these exosomes might inherit somemolecular components (Fais et al., Biol. Chem. 394:1 (2013)).Interaction between endothelial ICAM-1 and Mϕ LFA-1 mediates the lateralmigration and paracellular/transcellular diapedesis of Mϕs acrossendothelial barriers (Carman, J. cell Sci. 122:3025 (2009)). Previouswork also suggested that ICAM-1/LFA-1 mediated the uptake of Mϕ exosomesinto human umbilical vein endothelial cells (Jang et al., ACS Nano7:7698 (2013). Therefore, we examined the possible involvement ofICAM-1/LFA-1 in the uptake of Mϕ exosomes in hCMEC/D3 cells. First, weconfirmed the presence of LFA-1 in exosomes and ICAM-1 in hCMEC/D3 cellsby western blot (FIGS. 28A-28B). Second, we used LPS to stimulate ICAM-1expression in hCMEC/D3 cells (Li et al., J. Neuroinflammation 9:161(2012)), essentially mimicking in vitro a process that can take partduring inflammation in vivo. Following exposure to LPS, expression levelof ICAM-1 in hCMEC/D3 cells increased (FIG. 28B). This was companied bythe increase in the cell uptake of exosomes (FIG. 28C). Finally, wedemonstrated that each of anti-ICAM-1 or anti-LFA-1 antibodies inhibitedexosome uptake (FIG. 28D). Altogether, these experiments suggest thatthe exosomal integrin LFA-1 and endothelial ICAM-1 play an essentialrole in the uptake of Mϕ exosomes in hCMEC/D3 cells.

C-type lectin receptors mediated uptake of Mϕ exosomes in hCMEC/D3cells. During the endocytosis inhibition studies (FIGS. 26A-26D), wenoted that sucrose had a more profound inhibitory effect on the celluptake of Mϕ exosomes than that of transferrin. Therefore, we suspectedthat some carbohydrate binding receptors may be involved in the uptakeof exosomes. To evaluate this possibility, we examined the effects ofexposure of cells to non-toxic concentrations of various carbohydrateson the cell uptake of Mϕ exosomes (FIG. 30A). These effects wereobserved at the maximal and half-maximal tolerable concentrations thatensure at least 80% cell viability (FIG. 27 ). The tested carbohydratesinhibited cell uptake of exosomes to different extents. Among them,glucosamine inhibited the uptake at lower concentrations, suggestingthat the inhibitory effect differed from hyperosmolarity that is knownto block endocytosis (Oka et al., J. Biol. Chem. 264:12016 (1989)). Somecarbohydrates can inhibit ICAM-1 expression in some cells, such asglucosamine in rat cardiomyocytes (Zou et al., Am. J. Physiol. HeartCirculatory Physiol. 296:H515 (2009)) and human retinal pigmentepithelial cells (Chen et al., Invest. Ophthalmol. Visual Sci. 53:2281(2012)), and fucose in human keratinocytes (Palacio et al., Arch.Dermatol. Res. 289:234 (1997)). We selected two carbohydrates that haddifferent level of inhibition. However, even at highest concentrationused, glucose and glucosamine did not inhibit the expression of ICAM-1in our cell model (FIG. 31 ). Therefore, based on the analysis ofdifferent carbohydrates, we conclude that the uptake of Mϕ exosomes inhCMEC/D3 cells involves specific carbohydrate binding receptors.

One possible candidate of carbohydrate binding receptors that has beenreported for the uptake of exosomes is the C-type lectin receptors (Haoet al., Immunology 120:90 (2007)). The carbohydrate recognition domainsof C-type lectin receptors require binding of calcium for theircarbohydrate-binding activity (Drickamer, Curr. Opin. Struct. Biol.9:585 (1999); Cambi et al., Cell. Microbiol. 7:481 (2005)). It isreported that DCs internalized their secreted exosomes partially bymannose/glucosamine-binding C-type lectin receptors (Hao et al.,Immunology 120:90 (2007)), as demonstrated by blocking assay usingDEC205 antibodies, calcium chelator ethylenediaminetetraacetic acid(EDTA) and a panel of monosaccharides, especially mannose andglucosamine. Similarly, cell uptake of Mϕ exosomes in hCMEC/D3 cells wasdecreased by a panel of carbohydrates, ethyleneglycol-bis(2-aminoethylether)-N, N, N′, N′-tetraacetic acid (EGTA, ananalog to EDTA but has superior selectivity for calcium) (Sanui et al.,J. Cell. Physiol. 1967, 69:11 (1967)), and especially DEC205 antibodiesagainst 205 kD integral membrane protein homologous to the Mϕ mannosereceptor (FIGS. 30A-30C). The selected concentration of EGTA ensured atleast 80% cell viability (FIG. 27 ). Taken together, these experimentsconfirmed that carbohydrates-, especially glucosamine-binding C-typelectin receptors mediated the uptake of Mϕ exosomes in hCMEC/D3 cells.

PK and distribution of Mϕ exosomes in healthy mice. The in vivodistribution of tumor exosomes was previously studied by theirradiolabeling with ¹¹¹indium (Smyth et al., J. Controlled Release199:145 (2015)), or by incorporating fluorescent dyes (Smyth et al., J.Controlled Release 199:145 (2015)) or luciferase (Takahashi et al., J.Biotechnol. 165:77 (2013); Imai et al., J. Extracellular Vesicles4:26238 (2015)). In general, tumor exosomes were rapidly cleared by themononuclear phagocyte system (MPS). We quantitatively characterized thePK and distribution of Mϕ exosomes in healthy CD-1 mice by radiolabelingexosomal proteins with ¹²⁵I, a traditional method to track proteins andcells in vivo (Banks et al., J. Neuroinflammation 9:231 (2012)). Forthis study we collected Mϕ exosomes after 12 h incubation of Mϕ inserum-free medium (Dulbecco's modified eagle medium, DMEM) to excludeiodination of serum proteins that could be co-precipitated duringisolation of exosomes by ultracentrifugation. ¹³¹I-labeled bovine serumalbumin (BSA) was co-injected with ¹²⁵I-labeled Mϕ exosomes as avascular marker. The serum clearance of ¹²⁵I-exosomes and ¹³¹I-BSAshowed two-phase decay (FIG. 32A). The rate of serum clearance (Cl) andvolume of distribution at steady state (Vss) of co-injected BSA (Table3) were similar to previously published data (0.0035 ml/min and 1.5 ml)(Shinoda et al., J. Pharm. Sci. 87:1521 (1998)). It is reported thatexosomes from antigen-presenting cells can evade complement-mediatedlysis by expression of CD55 and CD59 (Clayton et al., Eur. J. Immunol.33:522 (2003)), which are present on monocytes/Mϕs (Christmas et al.,Immunology 119:522 (2006)). However, the mean residence time from thetime of dosing to last detectable concentration (MRT_(last)) and fromthe time of dosing to infinity (MRT_(inf)) of Mϕ exosomes was notimpressive when compared with the published data for PEGylated liposomes(Qhattal et al., ACS Nano 8:5423 (2014); Arndt et al., Breast CancerRes. Treat. 58:71 (1999); Brusa et al., Anticancer Res. 27:195 (2007);Gaddy et al., EJNMMI Res. 5:24 (2015); Shapiro et al., Antimicrob.Agents Chemother. 57:4816 (2013)). Similar to tumor exosomes (Smyth etal., J. Controlled Release 199:145 (2015)), Mϕ exosomes mainlyaccumulated in MPS organs, liver and spleen at 10 min, 4 h and 24 h(FIG. 32B), suggesting insufficient avoidance of MPS. Accumulation of Mϕexosomes in brain at 10 min and 4 h was 0.1% ID/g and decreased to 0.05%at 24 h, suggesting clearance-limited brain accumulation. Although thelimitation of our PK study in CD-1 mice was that the exosomes originatedfrom Raw Mϕs derived from BALB/c mice, we do not believe that the straindifference contributed to the accelerated clearance and poor brainaccumulation of the exosomes. It was previously suggested that thehomologous tumor exosomes still may not readily evade the immune system(Smyth et al., J. Controlled Release 199:145 (2015)). In addition,expression of ICAM-1 (Aoudjit et al., J. Immunol. 161:2333 (1998)) andlectin receptors (Vasta et al., Animal lectins: a functional view. CRCPress: Boca Raton, 2009; p xxii, 558 p., 16 p. of plates)⁶ in liver andspleen might contribute to the distribution of Mϕ exosomes to liver andspleen. Taken together, strategies such as PEGylation can be explored inthe future to shield exosomes and extend circulation in order to improvebrain accumulation.

TABLE 3 Noncompartmental PK parameters of Mϕ exosomes and BSA in healthyCD-1 mice. Cl (ml/min)* Vss (ml)* MRT_(last) (h)* MRT_(inf) (h)* ¹²⁵I-0.016 3.15 0.91 3.40 Exosomes ¹³¹I- 0.0039 1.44 0.94 6.10 BSA *Estimatedusing Phoenix ®WinNonlin ® 6.3 (Pharsight).

Inflammation increased brain influx rate and brain accumulation of Mϕexosomes. To examine whether the accumulation of Mϕ exosomes in theinflamed brain could increase, we compared the PK of Mϕ exosomes inhealthy mice and brain inflammation mouse model. This model wasestablished by intracranial injection of 10 μg of LPS a day before thePK study (Haney et al., PloS One 8:e61852 (2013); Zhao et al., J.Nanomed. Nanotechnol. S4 (2011)). The serum clearances of exosomes andco-injected BSA in the brain-inflamed mice resembled those in thehealthy mice (FIG. 33A). Delta brain/serum ratio was calculated bysubtracting the brain/serum ratio of BSA from that of exosomes tocorrect for vascular space (Banks et al., Brain Behav. Immun. 24:102(2010)). Both healthy and brain-inflamed mice showed significant netbrain influx of exosomes (FIG. 32C): the slopes (Ki) of deltabrain/serum ratio against exposure time significantly deviated from zero(p<0.05 by two-tailed t-test). However, the net brain influx rate (Ki)and volume of brain distribution (Vi) of exosomes in the brain-inflamedmice was 3 and 2 fold higher than those in the healthy mice,respectively. The plot of the delta brain/serum ratio against serumconcentration directly demonstrated increased accumulation of Mϕexosomes in the inflamed brains at similar serum concentrations (FIG.33B). In addition, the brain influx rates of BSA in the brain-inflamedand healthy mice were comparable (p=0.076, FIG. 33C), suggesting thatincrease in brain influx of exosomes under inflammation was not due toimpaired BBB function. Consistent with the increased brain influx rate,the brain accumulation of Mϕ exosomes in the inflamed brain at 10 minwas 5.8 fold higher than that in the healthy brain (FIG. 32D). This datawas consistent with the increased accumulation of exosomes in LPStreated hCMEC/D3 cells in vitro (FIG. 29D). As the expression of ICAM-1in brain endothelium increases during inflammation, the adhesion andpotentially brain uptake of exosomes through LFA-1 could also increase.This process may have some commonality with increased brain infiltrationof Mϕs upon inflammation (Batrakova et al., Exp. Opin. Drug Deliv. 8:415(2011); Gupta et al., J. Neuroinflammation 11:68 (2014); Shi et al.,Nature Rev. Immunol 11:762 (2011)). The brain-inflamed mouse model alsodisplayed significantly higher accumulation of Mϕ exosomes in the heart(1.6 fold), lung (7.1 fold) and kidney (3.9 fold) (FIG. 32D). This couldbe explained by peripheral inflammation resulting from the absorption ofLPS from the brain cerebrospinal fluid to blood (Banks et al., BrainBehav. Immun. 24:102 (2010)). The inflammation-responsive braindistribution of Mϕ exosomes is remarkable and provides strong rationalefor their potential application as natural nanocarriers forinflammation-related brain diseases.

Mϕ exosomes delivered BDNF to the inflamed brain. To determine whetherMϕ exosomes could deliver a therapeutic cargo to the brain, we loadedthe exosomes with BDNF by simple mixing in 10 mM phosphate buffer onice. BDNF can contribute to the neuronal survival and synapticplasticity by activating the tropomyosin receptor kinase B (TrkB) and isinvestigated as potential biotherapeutic agent to treatneurodegenerative and neurodevelopmental diseases including AD, PD,Huntington's disease and RETT syndrome as well as stroke (Nagahara etal., Nature Rev. Drug Discov. 10:209 (2011)). The complex betweenexosomes (zeta potential −18 mV) and BDNF (isoelectric point 9.99(Patterson et al., Neuron 16:1137 (1996)) was formed due toelectrostatic interactions as well as strong binding of BDNF topolysaccharides (Kanato et al., Glycobiology 18:1044 (2008); Kanato etal., Biosci. Biotechnol. Biochem. 73:2735 (2009)) that are displayed onthe exosomal surface. To confirm the binding of BDNF to exosomes, weused Protein G-magnetic beads coupled with BDNF antibodies to separateBDNF treated exosomes (FIG. 23E). A control experiment without BDNFtreatment was used to account for the nonspecific binding. Based on thepresence of the exosomal membrane protein LAMP 2 in the magnetic-beadsseparated fractions the exosomes were captured on the beads only aftertreatment with BDNF (FIG. 34A). To estimate the amount of BDNF that canbe loaded on the exosomes we analyzed various BDNF and exosome mixturesby native gel electrophoresis. In this experiment exosomes prevented theneurotrophin migration in the gel toward the anode up to a BDNF:exosomal proteins weight ratio of 1:5 (FIG. 34B). This further confirmedBDNF and exosomes complex formation and established that Mϕ exosomes cancapture as much as 20% wt. BDNF relative to its own protein.

We further determined if Mϕ exosomes would ferry BDNF to the brain. Inthis experiment we co-injected ¹³¹I-labeled BSA along with the¹²⁵I-labeled BDNF with or without exosomes into the jugular vein ofhealthy CD-1 mice. The delta brain/serum ratios of BDNF formulated withexosomes were significantly higher than those of BDNF alone (FIG. 35A).To the contrary, the brain influx rates of co-injected BSA in bothgroups were comparable and did not differ from 0 (FIG. 35B). This dataalso indirectly suggested that BDNF remained with exosomes afteradministration in vivo. We further compared the brain accumulation ofnative and exosomes formulated BDNF in healthy and brain-inflamed mice(FIG. 35C). The brain accumulation of exosome-formulated BDNF in healthymice was slightly but not significantly increased compared to BDNF alone(p=0.63). The brain inflammation resulted in a trend to increase thebrain accumulation of free BDNF but the difference was not significantwhen compared to the healthy mice (p=0.11). In contrast, accumulation ofexosome-formulated BDNF in the brain-inflamed mice was significantlyincreased compared to the same formulation in the healthy animals (3.6fold). Moreover, the brain accumulation of BDNF with this formulationwas also superior to that of the naked BDNF in the inflamed brain.

Conclusions

In summary, we demonstrated in vitro and in vivo that exosomes secretedfrom Raw Mϕs have potential as nanocarriers for the delivery oftherapeutic payload to the brain for treatment of inflammation-relatedbrain diseases. In vitro Mϕ exosomes were endocytosed into human brainendothelial cells in a receptor-dependent manner, which involvedICAM-1/LFA-1 and C-type lectin receptors, was increased in response tostimulation of the cells with LPS along with increased ICAM-1expression. In vivo Mϕ exosomes showed positive influx rate into thebrain, which was also increased along with the overall brain uptake inmouse brain inflammation model. Perhaps, even more importantly, wedemonstrated that Mϕ exosomes can deliver BDNF into the brain in thisinflammation model. This finding could provide opportunities fordeveloping of novel therapeutic modalities comprised ofneurotrophin-loaded Mϕs exosomes for treatment of CNS diseasesassociated with inflammation, such as AD, PD, and stroke (Batrakova etal., Exp. Opin. Drug Deliv. 8:415 (2011)).

Example 4 Exosomes as Carriers for Nucleic Acids

In this example exosomes isolated from macrophages are formulated withpolynucleotide pDNA using a cationic polymer as the third component ofthe formulation exosomes-pDNA-polycation. Without being bound to aspecific theory we believe that the polycation 1) condensespolynucleotide and 2) binds with the both the polynucleotide andexosomes (negatively charged) thereby increasing the stability of theexosomes-pDNA-polycation formulation. The resulting formulation is shownto efficiently deliver polynucleotide to the target cell resulting inexpression of the gene encoded by this polynucleotide.

Methods

Isolation of exosomes: Exosomes were isolated via a PEG method fromRAW264.7 cells that were grown until confluent. Briefly, media washarvested from the cells, supplemented with PEG 8000 solution andincubated at 4° C. overnight. Following the incubation, the solutionwith exosomes was centrifuged at 3200 rpm for 30 minutes. Thesupernatant was aspirated and spun at 3200 RPM for another 5 min toeliminate residual PEG. The procedure was repeated and all four pelletswere combines together and rehydrated in 100 μl phosphate bufferedsaline (PBS).

Loading of exosomes with pDNA: Exosomes suspension in PBS (25 μl) wassupplemented with saponin (5 μl stock solution) to the finalconcentration 0.26%, and incubated 15 min at room temperature (RT).Then, luciferase-encoding pDNA solution (10 μl, 2 μg/ml) was added andall mixture was incubated for another 15 min at RT. Following theincubation, 354.4 μl PBS and 5.6 μl linear polyethyleneimine (PEI)solution in PBS (final concentration 0.378 mg/ml) were added to theexosome suspension and incubated for another 15 min at RT. Obtainedexosomes with incorporated pDNA (exoDNA) were used in furtherexperiments.

Results

Transfection of target cells with exosome-incorporated pDNA: RAW 264.7cells were seeded in a 96-well plate. Various formulations ofluciferase-encoding pDNA (2 μg/ml): exoDNA, or naked pDNA, or pDNAcomplexed with PEI, or pDNA mixed with commercially available GenePORTER3000 transfection reagent (GP3K), were added to cell medium for 4 hours.Then, the cells were cultured for additional 20 hours in 10% serum at37° C., and the expression of luciferase in cell lysates were assessedby luminescence (FIG. 36 ). The luciferase expression in the cells wasexpressed in relative units per mg protein. DNA incorporation intoexosomes resulted in the three orders of magnitude increase in theencoded protein expression compared to naked DNA, and significantlygreater expression levels than in cells transfected with GP3K, or PEI.Noteworthy, the use of GP3K or PEI in clinic is restricted due to theirhigh toxicity.

Transport of pDNA formulated in exosomes to nuclei of target cells:Model pDNA was labeled with a fluorescent dye, YOYO, and then formulatedinto exosomes as described above. IC21 cells were incubated with exoDNAfor 4 hours, then cells were washed, permeabilized, nuclei were labeledwith DAPI. Intracellular distribution of exosomes (FIG. 37 ) wasvisualized by fluorescent confocal system ACAS-570 (MeridianInstruments, Okimos, Mich.). A considerable co-localization of pDNA andnuclei was evident in the images.

Optimization of exoDNA formulation: A relative amount of pDNA and PEIincorporated into exosomes was varied to estimate the best N/P +/−charge ratio resulted in optimal transfection rate. The N/P ratio wascalculated by dividing the amount of amino groups of PEI by the totalamount of negative phosphate groups of pDNA. Different compositions ofexosomes permeabilized with saponin and incubated withluciferase-encoded pDNA and PEI was prepared as described above, andtransfection efficacy in RAW 264.7 cells was examined (FIG. 38 ).

Expression of the encoded green fluorescence protein (GFP), inmacrophages transfected with exoDNA: IC21 macrophages were incubatedwith optimized exosome-based formulation of GFP-encoding pDNA (2 μg/mlpDNA, N/P ratio—12) for different time points. Then, the cells werewashed, fixed and permeabilized. The nuclei were stained with Hoechstreagent. Exosomes were stained with a fluorescent dye, DII before theloading with pDNA. The intracellular distribution of exosomes andoverexpressed GFP in IC21 cells was visualized by fluorescent confocalsystem ACAS-570 (Meridian Instruments, Okimos, Mich.). Exosomes werereadily taken up by IC21 cells in vitro. Considerable amount of theencoded protein, GFP, was detected in the transfected cells (FIG. 39 ).

Example 5 Cationized Exosomes for Delivery of siRNA to Cancer Cells

In this example, exosomes were modified with a cationic lipid containingmultiple positive charges to increase loading of polynucleotide into theexosomes. The exosomes were isolated from IC21 macrophages, thenmodified with the cationic lipid and then loaded with siRNA. Briefly,exosomes were collected by PEG precipitation from macrophage media(4.14×10² part/ml) and modified with cationic lipid, MVL5,N1-[2-((1S)-1-[(3-aminopropyl)amino]-4-[di(3-aminopropyl)amino]butylcarboxamido)ethyl]-3,4-di[oleyloxy]-benzamide)(Avanti Polar Lipids, Inc.) having a cationic headgroup that containsfive positively charged primary and secondary amines. To incorporate thelipid into the membranes of the exosomes, 1×10¹⁰ exosomes werere-suspended in 1 ml phosphate buffer 10 mM, pH 7.4 and supplementedwith 12 μl MVL5 lipid ethanol stock solution (1 mg/200 μl) in onealiquot, or the same volume of this solution in four 3 μl aliquots. Themixture was sonicated in an ultrasound bath for 7-10 min at 40-45° C.every time after the lipid aliquot addition, and then incubated at 37°C. for one more hour to allow for equilibration of the components. Oneportion of lipid-modified exosomes was permeabilized with 1.6% saponinin PBS.

To load siRNA in exosomes, a dispersion of 0.5 ml lipid-modifiedexosomes permeabilized with 1.6% saponin was supplemented with threeportions of 10 μl CY5-labeled siRNA reconstituted in siRNA buffer (20 μMstock solution of siRNA) and vortexed for 30 sec. The mixture was thenincubated for 1 hour at 37° C., and exosomes with incorporated siRNAwere purified from non-incorporated siRNA using Sepharose CL4B column(3.7 ml diameter 1 cm). Purified exosomes were collected in 8 fractions(0.5 ml each), and the level of fluorescence (CY5) in exosome fractionswas measured at ex 649 nm, em 675 nm using a 96-well-black clear bottomplate. The concentration of the exosomes was determined by the NTA usingNanosight NS500 (Malvern, UK) and the zeta-potential of the exosomes wasmeasured by DLS using Zetasizer Nano-ZS instrument (Malvern, UK).

To evaluate siRNA accumulation in MDA-MB-468 triple negative breastcancer cells, the cells were plated in 8-chamber slides one day prior tothe experiment. The cationic lipid-modified exosomes permeabilized with1.6% saponin and loaded with siRNA (siRNA-MVL5-saponin-exo) and allrelevant controls specifically, cationic lipid-modified exosomes loadedwith siRNA (siRNA-MVL5-exo); unmodified exosomes loaded with siRNA(siRNA-exo); exosomes modified with cationic lipid (siRNA-MVL5); andnaked siRNA were prepared in sterile PBS immediately prior to theexperiment Cells were incubated with siRNA formulations for 4 hours,washed thrice with PBS supplemented with 1 mg/mL heparin sulfate toremove unbound exosomes; and fixed for 15 min. at RT in 4.0%paraformaldehyde (PFA). Then, the cells were stained with 1:5000dilution of Hoechst nucleic acid counterstain, rinsed 3×, supplementedwith 200 μL of PBS, and imaged on a Zeiss 710 Confocal Microscope (FIG.40 ). The mean intensity of siRNA in the cells was analyzed by Image Jsoftware (FIG. 41 ).

The data demonstrate that the exosomes modified with cationic lipidcontaining multiple positive charges and loaded with siRNA enhancedelivery of the siRNA in cancer cells. The data also demonstrate that inthis approach the permeabilization of the exosomes with saponin prior toloading of siRNA is not necessary and in fact results in a decreaseddelivery of the siRNA in the cancer cells compared to exosomes that werenot permeabilized with saponin.

Example 6 Cationized Exosomes for Gene Delivery to Macrophages

In this example, exosomes were modified with a cationic lipid containingmultiple positive charges to increase loading of polynucleotide into theexosomes. The exosomes were isolated from IC21 macrophages, modifiedwith the cationic lipid and then loaded with either mRNA or pDNA eachencoding a reporter gene, luciferase. Then exosomes loaded with eithermRNA or pDNA were used for gene delivery to cells.

To prepare the cationized exosomes the exosomes were collected by PEGprecipitation from IC21 macrophages media (2.9×10¹¹ part/ml) andmodified with cationic lipid, MVL5. To incorporate the lipid intoexosomal membranes, 2.9×10¹¹ exosomes were re-suspended in 1 mlphosphate buffer 10 mM, pH 7.4 and supplemented with 2 μl MVL5 lipidethanol stock solution (5 mg/ml) four times (total lipid added 8 μl or40 μg (7.14×10⁴ molecules lipid/exosome). The mixture was sonicated inan ultrasound bath for 7-10 min at 40-45° C. every time after the lipidaddition, and incubated at 37° C. for 30 min. Then, exosomes weresupplemented with 40% 8 kDa PEG solution in PBS for 4 hours at 4° C.Following incubation, cationized exosomes were collected bycentrifugation for 30 min at 4000 RPM, and the exosomal pellet wasreconstituted in 442 μL PBS (to match GP3K control volume).

As the next step the cationized exosomes were loaded with either thefirefly luciferase expressing mRNA, Luc-mRNA (TriLink Biotechnologies,San Diego, Calif.) or the pDNA gWIZ™ Luc, a gWIZ™ high expression vectorencoding the reporter genes luciferase under control of an optimizedhuman cytomegalovirus (CMV) promoter followed by intron A from the CMVimmediate-early (IE) gene (Gene Therapy Systems, San Diego, Calif.). Toload the cationized exosomes with mRNA or pDNA expressing luciferase,the 0.2 ml of aqueous dispersion containing 1×10¹ of the cationizedexosomes modified with MVL5 lipid was supplemented with 2 μl of 2 μgLuc-mRNA or 2 μg pDNA in PBS and incubated for 30 min at 37° C. Thisresults in the formation of the mRNA and pDNA complexes with thecationized exosomes.

The ability of mRNA or pDNA loaded cationized exosomes to transfectcells was examined using Raw 264.7 macrophages. The cells were seeded on24-well plate one day prior to the experiment. The cationiclipid-modified exosomes loaded with mRNA (EXO+RNA) or pDNA (EXO+DNA) andall relevant controls, including mRNA formulated with GenePorter 3000(GP3K mRNA); pDNA formulated with GenePorter 3000 (GP3K DNA); or nakedmRNA (mRNA Only); and naked pDNA (DNA Only) were prepared in sterile PBSimmediately prior to the transfection experiment. Cells were incubatedwith mRNA and pDNA formulations for 4 hours, washed thrice with PBS, andsupplemented with full media for another 24 hours. Then, the cells werelysed and the luciferase levels were determined using a luminometer(FIG. 42 ).

The data suggest that that both mRNA and pDNA complexes with thecationized exosomes can efficiently transfect Raw 264.7 macrophagesresulting in expression of the luciferase reporter gene. The luciferaselevels in cells transfected by exosome-based formulations of mRNA andpDNA were significantly greater than in those treated with naked mRNAand pDNA, respectively.

Example 7 Exosomes Expressing GDNF for Treatment of Transgenic MouseModel of PD

In this example exosomes were isolated from genetically modifiedmacrophages that were transfected with plasmid DNA (pDNA) encoding GDNF.The resulting GDNF-exosomes carried the DNA, RNA and/or protein producedin the genetically modified macrophages as a result of theirtransfection with the GDNF-encoding pDNA. The exosomes were then usedfor the delivery of these biological agents and GDNF to the inflammationsite in the brain to treat PD.

As the first step IC21 macrophages were transfected with theGDNF-encoding pDNA. To obtain the pDNA the human GDNF cDNA NM_199234(OriGene Rockville, Md.) was expanded in DH5a E. coli and isolated usingQiagen endotoxin-free plasmid Giga-prep kits (Qiagen, Valencia, Calif.)according to the supplier's protocol. Briefly, macrophages grown in T-75flasks (20×10⁶ cells/flask) were incubated with a mixture of 13.6 μgGDNF-encoding pDNA formulated with cationic lipid based transfectionsystem GenePorter 3000 (GP3K) in serum free media for 4 hours. Followingincubation, an equal volume of full media containing 20% FBS was addedbringing the final serum concentration to 10%. Then, macrophages werecultured in FBS-exosome-depleted media for 24 hours; to avoidcontamination of the FBS-derived exosomes, FBS was spun at 100,000×g for2 hours to remove exosomes before use. Following the incubation,exosomes were harvested from genetically modified macrophages mediausing the ExoQuick-TC™ Kit (System BioSciences; Mountain View, Calif.)and washed twice with PBS. The recovery of exosomes was determined bymeasuring the protein concentration using the Bradford assay and by NTA(10¹¹-10¹² exosomes/flask). The obtained GDNF-exosomal fraction wasre-suspended in PBS (500 μl, 1 mg/mL total protein), and exosomeparticle size was determined by NTA; the average diameter was 100.9 nm.

Next, GDNF-exosomes were administered in Parkin Q311X(A) transgenic mice(4 months old) through intravenous (i.v.) or intranasal (i.n.) routes ata dose of 1×10¹⁰ GDNF-exosomes per mouse three times every week. Afterone-month of treatment behavioral studies were performed every month forfive months. Healthy non-carriers, as well as PD mice injected withsaline were used as control groups. Hanging wire (FIG. 43A), rotarod(FIG. 43B) and escaping activity (FIG. 43C) tests were performed. ParkinQ311X mice treated with GDNF-exosomes demonstrated significantimprovements in motor skills compared to the control saline-treatedcarriers. The performance in Parkin group treated with GDNF-exosomes wassimilar to healthy controls (FIGS. 43A-43C). The data demonstrate thatGDNF-exosomes exhibit therapeutic activity in the transgenic mouse modelof PD.

Example 8 Increased Production of Exosomes from Cells Treated by theBlock Copolymer

In this example, the production of exosomes by IC21 macrophages wassignificantly increased as a result of the treatment of the cells withPluronic® block copolymer. Briefly, cells grown in T25 flasks (2×10⁶cells/flask) were incubated with 1% Pluronic® P85 (PEO-PPO-PEO triblockcopolymer with average molecular mass 4600, total weight content of PEOblocks 50%, HLB from about 12 to about 18) solution for four hours.Following the incubation, the cells were washed 3×PBS, and cultured inserum-free media for another 20 hours. Macrophages incubated inPluronic-free media were used as a control. Exosomes were collected byPEG precipitation from macrophage concomitant media and the number ofparticles was accessed by NTA. The treatment with Pluronic® P85significantly increased the amount of exosomes released by IC21macrophages (FIG. 44 ).

Example 9 Increased Transfecting Activity of Exosomes from GeneticallyModified Cells Treated by Block Copolymer

In this Example Exosomes were Isolated from the Genetically Modifiedmacrophages that were transfected with the plasmid DNA (pDNA) ormessenger RNA (mRNA), both encoding luciferase. To increase productionof exosomes the genetically modified macrophages prior to isolation ofthe exosomes were treated with Pluronic® block copolymer.

As the first step, donor Raw 264.7 macrophages were transfected withluciferase-encoding pDNA or mRNA. gWIZ™ Luc, a gWIZ™ high expressionvector encoding the luciferase reporter gene under control of anoptimized human cytomegalovirus (CMV) promoter followed by intron A fromthe CMV immediate-early (IE) gene (Gene Therapy Systems, San Diego,Calif.) was used as pDNA, and the firefly luciferase encoding mRNA,Luc-mRNA (TriLink Biotechnologies, San Diego, Calif.) was used as mRNA.Briefly, Raw 264.7 macrophages grown in T75 flasks (8.0×10⁶ cells/flask)were incubated in 12 mL RPMI 1640 serum-free media (SFM) with sixdifferent treatment solutions: flask #1 and #2) SFM (3008 μL RPMI 1640);flask #3 and #4) GP3K prepared as follows: a mixture of 14 μl SFM wasadded to 2.04 ml GP3K diluent; in parallel 192 μl GP3K reagent was addedto 762 μl SFM; serum-free media/reagent mixture was added to diluentmixture and incubated for 15 min at RT before adding to the cells; flask#5) GP3K prepared as follows: a mixture of 14 μg mRNA was added to 2.04ml GP3K diluent; in parallel 192 μl GP3K reagent was added to 762 μlSFM; serum-free media/reagent mixture was added to diluent mixture andincubated for 15 min at RT before adding to the cells; flask #6)GenePorter 3000 (GP3K) prepared as follows: a mixture of 14 μg pDNA wasadded to 2.04 ml GP3K diluent; in parallel 192 μl GP3K reagent was addedto 762 μl SFM; serum-free media/reagent mixture was added to diluentmixture and incubated for 15 min at RT before adding to the cells. Cellswere incubated at 37° C. with these mixtures for 4 hours. Following theincubation, the cells were washed 2× with serum-free media that wassupplemented with heparin sulfate (1 mg/ml).

As the second step, each flask containing Raw 264.7 cells was treated asfollows: #1) 10 mL SFM, #2) 10 mL SFM supplemented with 0.5% Pluronic®P85, #3) 10 mL SFM, #4) 10 mL SFM supplemented with 0.5% Pluronic® P85,#5) 10 mL SFM supplemented with 0.5% Pluronic® P85, #6) 10 mL SFMsupplemented with 0.5% Pluronic® P85. The cells were incubated withthese solutions for 18 hours.

After incubation the exosomes were isolated from the treated cellsconcomitant media by PEG precipitation. For this purpose, media wascollected from the cells, and centrifuged at 500 g for 5 min to removelive cells. Next, supernatant was collected and centrifuged again at4000 g for 15 min to remove cellular debris. Supernatant was thenfiltered through a 0.22 μm syringe filter, and 8 KDa PEG was added to afinal concentration 10%. Then, the mixture was incubated overnight (18hours) at 4° C., and centrifuged at 4000 g for 1 hour to precipitateexosomes. Supernatant was gently aspirated and the exosome pellet wascentrifuged again at 4000 g for 5 min to remove any remaining PEGsolution. Then, the exosome pellet was re-suspended in 100 μl PBS. Theresulting exosome solutions were #1) exosomes from untreated cells, #2)exosomes from Pluronic® P85-treated cells, #3) exosomes fromGP3K-treated cells, #4) exosomes from GP3K and Pluronic® P85-treatedcells, #5) exosomes from (GP3K+pDNA) and P85-treated cells, #6) exosomesfrom (GP3K+mRNA) and Pluronic® P85-treated cells.

As the final step, recipient IC21 macrophages were supplemented with theexosomes isolated from different treatment groups of Raw 264.7 cells.Briefly, IC21 macrophages seeded in 24-well plates (100,000 cells/well)were supplemented with different exosomes (2.5×10⁹/well) collected fromsix groups Raw 264.7 macrophages (treated as described above), andincubated at 37° C. for another 18 hours. Next, the cells were lysed andassessed for luciferase. As seen in this example exosomes produced bythe donor Raw 264.7 macrophages that were genetically modified with mRNAdid not show any detectable level of transfection of the recipient cells(FIG. 45 ). Only the exosomes released by the Raw 264.7 macrophages thatwere genetically modified with pDNA and treated with Pluronic® P85efficiently transfected IC21 macrophages (FIG. 45 ). This exampledemonstrates that functionally active exosomes can be produced by firsttransfecting a donor cell with a polynucleotide that is normally notpresent in these exosomes and culturing cells with Pluronic® P85.

Example 10 Accumulation of Exosomes from Human Pluripotent Stem Cells inMouse Lune Metastases

In this example exosomes were isolated from human pluripotent stem cellsand then used for in vivo delivery to lung metastases in a mouse.Concomitant media from human pluripotent stem cells (hiPSC) grown in 75Tflasks (20×10⁶ cells/flask) was collected, and exosomes were isolatedusing gradient centrifugation. In brief, the culture supernatants werecleared of cell debris and large vesicles by sequential centrifugationat 300 g for 10 min, 1000 g for 20 min, and 10,000 g for 30 min,followed by filtration using 0.2 μm syringe filters. Then, the clearedsample was spun at 100,000 g for one hour to pellet the exosomes, andsupernatant was collected. The collected exosomes (10¹¹-10¹²exosomes/flask) were washed twice with phosphate buffer solution (PBS).

Exosomes were characterized by NTA analysis (FIG. 46 ) and western blot(FIG. 47 ). The average size of exosomes was 101 nm. Exosomes from hiPSCshowed significant amounts of exosome-associated protein flotilin, aswell as LFA-1 as detected by western blot.

To establish lung metastases model in a mouse, 8FlmC-FLuc-3LL-M27 cells(5×10⁶ cells/mouse in 100 μL saline) were injected i.v. via the tailvein in groups of C57BL/6 mice (n=4). The tumor lung metastases wereallowed to establish for 10-12 days. Twelve days after the cancer cellswere injected, DID-labeled exosomes isolated from hiPSC wereadministered intranasally (i.n.) at a dose of 10⁷ particles/10 μl ineach nostril (×2) to mice with lung metastases. Four hours later, micewere sacrificed, perfused, lungs were extracted and sectioned on amicrotome at a thickness of 20 μm; nuclei were stained with DAPI (300mM, 5 min). The images of lung sections were examined by a confocalfluorescence microscopic system ACAS-570 and corresponding filter set,and processed using ImageJ software (FIG. 48 ). Confocal images revealedthat 4 h after administration exosomes were co-localized with lungmetastases as manifested in yellow color (FIG. 48 ).

Example 11 Engineered Exosomes for Targeted Delivery of Paclitaxel toPulmonary Metastases

In this example a formulation of PTX-loaded exosomes with incorporatedanisamide-polyethylene glycol (AA-PEG) vector moiety to target the sigmareceptor, which is overexpressed by lung cancer cells, was developed andoptimized. The AA-PEG-vectorized exosomes loaded with PTX(AA-PEG-exoPTX) possessed a high loading capacity, profound ability toaccumulate in cancer cells upon systemic administration, and improvedtherapeutic outcomes.

Methods

Reagents.1,2-distearoryl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethyleneglycol-2000)ammonium salt (DSPE-PEG) and DSPE-PE-anisamide (DSPE-PEG-AA) were agenerous gift from Dr. L. Huang (University of North Carolina at ChapelHill, N.C., USA). DSPE-PEG-NH2 was purchased from NOF AmericaCorporation (White Plains, N.Y., USA). 4-Methoxybenzoyl chloride,2-Bromoethylamine hydrobromide, benzene, sodium hydroxide, acetonitrile,N,N-Diisopropylethylamine (DIPEA), ether, and methanol were allpurchased from Sigma-Aldrich (St. Louis, Mo., USA). A lipophilicfluorescent dye, 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindo-carbocyanineperchlorate (DiL), was purchased from Invitrogen (Carlsbad, Calif.,USA). A sigma receptor ligand, anisamide (AA), and Triton X-100 wereobtained from Sigma-Aldrich (St. Louis, Mo., USA). Cell culture mediumand fetal bovine serum (FBS) were purchased from Gibco LifeTechnologies, Inc. (Grand Island, N.Y., USA). Culture flasks and disheswere from Corning Inc. (Corning, N.Y., USA). ExoQuick-TC™ ExosomePrecipitation Solution was obtained from System Biosciences (MountainView, Calif., USA). LysoTracker Green DND-26, ER-Tracker Blue-White DPX,and MitoTracker Deep Red were purchased from Invitrogen (Waltham, Mass.,USA).

Cell Culture. RAW 264.7 macrophages (purchased from ATCC, Manassas, Va.,USA) were cultured in Dulbecco's modified Eagle's medium (DMEM) highglucose (Gibco, Grand Island, N.Y., USA) supplemented with 10% fetalbovine serum (FBS; Thermo Fisher Scientific), 1% penicillin andstreptomycin at 37° C. and 5% CO₂. Murine Lewis Lung Carcinoma cellsubline (3LL-M27), a highly metastatic lung clone, a generous gift fromDr. L. Pelletier (CHUL, Laval University, QC, Canada), murine lungadenocarcinoma cells (344SQ), a generous gift from Dr. Pecot (UNC atChapel Hill, USA), as well as human small-cell lung carcinoma cells(H69/AR), human non-small cell lung carcinoma cells (A549), and normalhuman lung fibroblasts (Hel 299) were cultured in DMEM high glucosesupplemented with 10% FBS, 10 mM HEPES, 1% penicillin and streptomycinat 37° C. and 5% CO₂.

Animals. The experiments were performed with female C57BL/6 mice(Charles River Laboratories, Durham, N.C., USA) eight weeks of age instrict accordance with the recommendations in the Guide for the Care andUse of Laboratory Animals of the National Institutes of Health. Theprotocol was approved by the Committee on the Ethics of AnimalExperiments of the University of North Carolina at Chapel Hill. Theanimals were kept five per cage with an air filter cover under light-(12-hours light/dark cycle) and temperature-controlled (22±1° C.)environment. All manipulations with the animals were performed under asterilized laminar hood. Food and water were given ad libitum.

Exosome Isolation. For all studies, exosome-depleted media was preparedby ultracentrifugation of fetal bovine serum (FBS) at 120,000×g for 110min to remove all vesicular content, prior to addition to culture media.Exosomes were harvested from the supernatants of RAW 264.7 cellscultured in exosome-depleted media using the ExoQuick-TC™ Kit (SystemBioSciences; Mountain View, Calif., USA). Briefly, >90% confluent RAW264.7 cells were cultured in exosome-depleted media for 2 days. 50 mLconditioned cell culture media were centrifuged at 300×g for 10 min(Thermo CL-10 centrifuge with 0-G26/1 rotor, Thermo Fisher Scientific,Waltham, Mass., USA) in order to remove cells and cellular debris. Thesupernatant was then taken, filtered with a 0.22 μm PES filter, andExoQuick-TC™ Exosome Precipitation Solution (System Biosciences,Mountain View, Calif., USA) was added to the filtered supernatant andthe mixture was vortexed and incubated overnight at 4° C. Afterovernight incubation, the mixture was vortexed and subsequentlycentrifuged at 1500×g for 30 min. and 5 min. to pellet exosomes. Thesupernatant was discarded and the exosome pellet was re-suspended inPBS. Freshly prepared exosomes or exosomes stored at −20° C. were usedfor all experiments.

Preparation of AA-Vectorized Exosomes Targeted to the Sigma Receptor.Exosomes targeted to sigma receptor with DSPE-PEG-AA (AA-PEG-exo) andnon-vectorized control exosomes with DSPE-PEG (PEG-exo) were prepared asfollows: exosomes were isolated from macrophage media as described aboveand then DSPE-PEG or DSPE-PEG-AA (50 μg/ml) were added to the exosomemixture (for PEG-exo and AA-PEGexo, respectively). 100 μL of 10 mg/mLPTX in EtOH was also added to the mixture to load into exosomes. Themixtures were then sonicated by the same method described previously(Kim et al., Nanomedicine 12: 655-664 (2016)). Briefly, the mixture wassonicated using a Model 505 Sonic Dismembrator with 0.25″ tip (ThermoFisher Scientific, USA) with the following settings: 20% amplitude, 6cycles of 30 s on/off. After sonication, the AA-PEGexo or PEGexo orAA-exoPTX solutions were incubated at 37° C. for 60 min to allow forrecovery of the exosomal membrane.

Exosomes were purified from the excess of free DSPE-PEG or DSPE-PEG-AAby size exclusion chromatography using a NAP-10 Sephadex G25 column (GEHealthcare, Buckinghamshire, UK) according to the manufacturer'srecommended protocol. Briefly, 750 μL of AA-PEGexo or AA-exo were addedto the NAP-10 column and the void volume was discarded. 250 μL of PBSwas then added to the column and allowed to enter the gel bedcompletely. 1.2 mL of PBS was then added to the column and the eluatecontaining purified exosomal formulations was collected and stored at−20° C.

Characterization of AA-Vectorized Exosomes. Nanoparticle TrackingAnalysis (NTA). Exosomes were identified and characterized using aNanoSight LM 10 instrument (NanoSight Ltd., Amesbury, UK). The settingswere optimized and kept constant between samples, and each video wasanalyzed using the Nanosight system to obtain the size and concentrationof exosomes. The stability of exosomes was monitored by measuring sizeover a period of time under various conditions (4° C., room temperature,or 37° C.). Prior to measurement, exosomes were diluted 1:1000 to yielda particle concentration in the region of 108 particles/mL, inaccordance with the manufacturer's recommendations. All samples wereanalyzed in triplicate.

Dynamic Light Scattering (DLS). The average hydrodynamic diameter andzeta potential of exosomes was measured by DLS using a Malvern ZetasizerNano ZS system (Malvern, Worcestershire, UK) equipped with He—Ne laser(5 mW, 633 nm) as the light source at 22° C. All samples were analyzedin triplicate.

Western Blot Analysis. The levels of proteins constitutively expressedin exosomes, Alix and flotillin 1, as well as the lymphocyte functionassociated antigen-1 (LFA-1, subunit CD11a), were examined by westernblot analysis. Protein concentrations were determined using a BCA kit(Pierce Biotechnology, Rockford, Ill.). The protein bands were detectedwith Alix, flotillin 1, and CD11a primary monoclonal antibodies, (Abcam,Cambridge, UK; 1:1000 dilution), and secondary HRP-conjugated rabbitanti-goat IgG-HRP (Santa Cruse, Calif., USA; 1:5000 dilution). TheTSG101 levels were visualized by TSG101 monoclonal antibodies, Abcam(Cambridge, Mass., USA). The protein bands were visualized bychemiluminescent substrate (Pierce Biotechnology, Rockford, Ill., USA)and quantified using ImageJ software (National Institute of Health,Bethesda, Md., USA). To correct for loading differences in cellularlysates and exosomal fractions, the levels of proteins were normalizedto constitutively expressed β-actin in cells with goat polyclonalantibodies to β-actin (Abcam, ab8229; 1:500 dilution); and TSG101 inexosomes with goat polyclonal antibodies to TSG101 (Santa Cruz, S.C.6037; 1:200 dilution).

Membrane Fluidity Measurements. BODIPY-PC, a fluorescent dye, was usedas a probe to examine the effect of incorporation DSPE-PEG-AA on thefluidity properties of exosomal membranes as described earlier (Thery etal., Curr Protoc Cell Biol, Chapter 3: Unit 3 22C, (2006)). Briefly, 30μl exosomes with a concentration of 4×10¹¹ particles/ml were mixed with20 μl BODIPY-PC (0.03 mg/ml) and supplemented with 70 μl deionizedwater; the mixture was incubated for 45 min 37 C in darkness. Unboundlabel was removed by Zeba™ column (Life Technologies). The obtainedexosomal mixture was sonicated by one or six cycles US in the presenceof various amounts of DSPE-PEG-AA with or without PTX, and the membranefluidity was accessed by fluorescence of incorporated BODIPY-PC.Fluorescence intensities were measured with a Spectramax M5 platereader. An excitation wavelength of 495 nm and an emission wavelength of502 nm were used for both probes.

Drug Loading and Optimization AA-PEG-exoPTX. For PTX loading intovectorized exosomes, 1 mL of purified exosomes (˜10¹¹ exosomes) in PBSwas mixed with PTX and DSPE-PEG-AA. For this purpose, first PTX (10mg/mL drug in EtOH stock solution) was added to 1 mL exosomes in PBS.Then, different amounts of AA-PEG-DSPE (0.05-0.50 mg/ml) in PBS wereadded to the mixture of exosomes with PTX. The obtained mixture wassonicated using a Model 505 Sonic Dismembrator using a 0.25″ tip (ThermoFisher Scientific, USA) with the following settings: 20% amplitude, 6cycles of 30 s on/off for three minutes with a two-minute cooling periodbetween each cycle. After the sonication, solutions of AA-vectorizedexosomes loaded with PTX (AA-PEG-exoPTX) were incubated at 37° C. for 60minutes to allow for recovery of the exosomal membrane. Excess free PTXand AA-PEG-DSPE was separated from AA-PEG-exoPTX by size exclusionchromatography using a NAP-10 Sephadex G25 column (GE Healthcare,Buckinghamshire, UK) according to the manufacturer's protocol. Briefly,750 μL of AA-PEG-exoPTX were added to the NAP-10 column and the voidvolume was discarded. 250 μL of PBS was then added to the column andallowed to enter the gel bed completely and the eluate was discarded.1.2 mL of PBS was then added to the column and the eluate containingpurified AA-PEG-exoPTX was collected and stored at −20° C.

Quantification of Drug Loading by High Performance Liquid Chromatography(HPLC). The amount of PTX loaded into exosomes was measured by HPLCmethod as described earlier (Kim et al., Nanomedicine 12: 655-664(2016)). Briefly, AA-PEG-exoPTX or exoPTX (˜10¹⁰ exosomes/0.1 mL) in amicrocentrifuge tube was placed on a heating block set to 75° C. toevaporate solvent. After all solvent had evaporated, an equal volume ofacetonitrile was added to the tube and the mixture was vortexed,sonicated, and vortexed again. The sample was then centrifuged at 13,000rpm (Thermo Legend Micro 21, Thermo Fisher Scientific, Waltham, Mass.,USA) for 10 min. Following centrifugation, the supernatant was taken andfiltered through a Corning Regenerated Cellulose 0.2 μm syringe filterand transferred into HPLC autosampler vials. 20 μL aliquots wereinjected into the HPLC system (Agilent 1200, Agilent Technologies, PaloAlto, Calif., USA). All analyses were performed using a C18 column(Supelco Nucleosil C18, 250 mm×4.6 mm, 5 μm, 100 Å, Sigma-Aldrich) witha mobile phase of H₂O:acetonitrile (45:55, v/v) at a flow rate of 1mL/min at 30° C. Absorbance was measured at 227 nm to monitor theelution of PTX. The area under the PTX peak was measured for each sampleand compared with known concentration of standard. A calibration curvewas constructed by plotting peak area versus concentrations of PTX andwas found to be linear within the tested concentration range (r2=0.997).Exosome protein content was measured using the Pierce BCA Protein AssayKit (Thermo Fisher Scientific, Waltham, Mass., USA) according to themanufacturer's recommended protocol. Loading capacity is expressed by μgprotein of exosomes.

Accumulation of AA-Vectorized Exosomes in 3LL-M27 Cancer Cells in vitro.To determine the uptake of AA-vectorized exosomes (AA-PEG-exo) ascompared to empty exosomes (exo) and control PEGylated exosomes withoutanisamide (PEG-exo), 3LL-M27 cells were seeded overnight at 50,000cells/well in a 96-well plate. Exosomes (exo, PEG-exo, AA-PEG-exo) werelabeled with DiL dye. Briefly, exosomes were incubated with DiL (2 μM)at 37° C. for 20-30 min. Afterwards, excess free dye was separated fromlabeled exosomes by size exclusion chromatography using a NAP-10Sephadex G25 column (GE Healthcare, Buckinghamshire, UK) according tothe manufacturer's recommended protocol as described above. Anequivalent number of DiL-labeled exosomes (˜108 particles/well) wereadded to 3LL-M27 cells and incubated for varying lengths of time.Afterwards, the treatment solutions were removed and cells were washed3× with PBS. 1% Triton X-100 was then added to each well and the 96-wellplate was placed at −80° C. for 5 min and then shaken at 37° C. for 1h.The fluorescence in cell suspensions was measured by a Shimadzu RF5000fluorescent spectrophotometer. The suspensions were also analyzed forprotein content by BCA Assay using the Pierce BCA Protein Assay Kit(Thermo Fisher Scientific, Waltham, Mass., USA) according to themanufacturer's recommended protocol. Results were given as number ofexosomes per μg protein vs. time.

Receptor Competitive Inhibition. To determine whether AA-vectorizedexosomes to sigma receptor were accumulated in cancer cells viareceptor-mediated endocytosis, a receptor competitive inhibition studywas carried out. For this purpose, first a lipophilic fluorescent dye,DiL, was incorporated into exosome membranes. Briefly, the supernatantof RAW 264.7 macrophage conditioned media free of cells and cellulardebris was filtered with a 0.22 μm PES filter and incubated with DiL dye(4 μM) at 37° C. for 20 min. Following a 20-minute incubation,ExoQuick-TC™ exosome precipitation solution was added to the filteredsupernatant, the mixture was vortexed, and incubated overnight at 4° C.Then, the mixture was vortexed again and subsequently centrifuged at1500×g for 30 minute to pellet exosomes. The supernatant was discardedand the exosome pellet was re-suspended in PBS. Freshly-preparedfluorescently labeled exosomes or exosomes stored at −20° C. were usedfor all experiments.

Next, 3LL-M27 cells were seeded overnight at 50,000 cells/well in a96-well plate. Anisamide (AA) stock solution was prepared using DMSO anddiluted to working concentration in cell culture media. Cells werepre-treated with AA in media at varying concentrations for 30 min.Afterwards, media was removed from wells, and solutions of DiL-labeledAA-PEG-exo supplemented with free AA at varying concentrations wereadded to the cells and incubated for one hour. Cells were washed 3× withPBS, and supplemented with 1% Triton X-100. The fluorescence levels incell suspensions were measured by a Shimadzu RF5000 fluorescentspectrophotometer, and adjusted for protein content analyzed by BCAAssay using the Pierce BCA Protein Assay Kit (Thermo Fisher Scientific,Waltham, Mass., USA). Results were plotted as number of accumulatedexosomes/μg protein vs. concentration of free AA.

Effect of Proteinase K Treatment on Exosome Uptake in 3LL-M27 CancerCells in vitro. Exosomes possess a variety of surface proteins which arebelieved to play a significant role in cell uptake and adhesion, such astetraspanins (CD63, CD81, CD9), heat shock proteins (Hsc70), lysosomalproteins (Lamp2b) and fusion proteins (CD9, flotillin, Annexin) (Lotvallet al., J Extracell Vesicles 3: p. 26913 (2014)). In order to explorethe role of surface proteins on the exosome-based formulations uptake,samples of non-vectorized exosomes (exo), or AA-vectorized exosomes(AA-PEG-exo) were prepared at the same concentration (˜10¹¹ exosomes/mL)and treated with Proteinase K. Briefly, 10 μL of 10 mg/mL proteinase Kor PBS (as a control) were added to 1 mL DiL-labeled exo or AA-PEG-exoand incubated at 37° C. for 30 min. Excess free enzyme and dye wasseparated from digested exosomes by size exclusion chromatography usinga NAP10 column packed with Sepharose CL-6B. Briefly, 750 μL exosomeswere added to the column and the void volume was discarded. 250 μL ofPBS was then added to the column and allowed to enter the gel bedcompletely and the eluate was discarded. 1.2 mL of PBS was then added tothe column and the eluate containing purified exosomes was collected andstored at −20° C.

Next, 3LL-M27 cells were seeded overnight in a black/clear bottom96-well plate (Corning Costar, Corning, N.Y., USA) at 50,000 cells/well.Proteinase K-treated DiL-labeled exosomes and non-treated exosomes as acontrol were diluted to the same concentration and added to wells forvarying lengths of time. After two hours, media was removed, cells werewashed 3× with PBS, and supplemented with 1% Triton X-100(Sigma-Aldrich, St. Louis, Mo., USA). The fluorescence levels in cellsuspensions were measured using a Spectramax M5 microplate reader(Molecular Devices, Sunnyvale, Calif., USA) at λex=540 nm and λem=570nm, and compared against a known concentration of standard. Acalibration curve constructed by plotting peak area versusconcentrations of DiL labeled exosomes was found to be linear within thetested concentration range (r²=0.999). Exosomal protein content wasmeasured using the Pierce BCA Protein Assay Kit (Thermo FisherScientific, Waltham, Mass., USA). Results were expressed as number ofaccumulated exosomes per μg protein vs time.

Intracellular Trafficking of Exosomes. In order to assess theintracellular trafficking of exosomes, 3LL-M27 cells were seeded at500,000 cells/well in chamber slides and incubated overnight.AA-vectorized (AA-exo) and non-vectorized exosomes (exo) were labeledwith DiL as described above, and added to cells for varying times. Mediawas then removed, and pre-warmed staining solutions (ER TrackerBlue-White DPX, or LysoTracker Green DND-26, or MitoTracker Deep Red)were added to the cells according to the manufacturer's recommendedinstructions. Then, cells were washed 3× with PBS, and fixed by theaddition of Formal-Fixx for 20 min at 37° C. Exosomes and organelleswere visualized by confocal fluorescence microscopic system ACAS-570(Meridian Instruments, Okimos, Mich., USA) with argon ion laser andcorresponding filter set. Excitation/emission were set and measured at540 nm/570 nm for DiL-labeled exo and AA-exo, and 358 nm/461 nm, or 490nm/520 nm, or 640 nm/670 nm for ER Tracker Blue-White DPX, LysoTrackerGreen DND-26, and MitoTracker Deep Red, respectively.

Biodistribution of Intravenously Injected Exosomes in Mice withPulmonary Metastases. To utilize fluorescence imaging, 3LL-M27 cellswere transduced with lentiviral vectors encoding the optical reporterFITC (FITCFlmC, green) fluorescent protein as reported earlier(Sena-Esteves et al., Journal of Virological Methods; 122(2):131-9(2004)). The viral construct also encoded for a puromycin resistancegene downstream of FITC, which was introduced to enable for theselection of positively transduced cells. C57BL/6 mice (n=4) wereinjected intra tail vein (i.v.) with FITC-FLmC-3LL-M27 cells (5×10⁶cells/mouse in 100 Al saline) and tumor lung metastases were allowed toestablish for 10-12 days. In parallel, exosomes isolated from autologousmacrophages conditioned media were stained with a fluorescent lipophilicdye DiD (red) and vectorized to the sigma receptor with DSPE-PEG-AA.Twelve days following cancer cells i.v. injection, DiD-labeledAA-PEG-exo formulation was administered intravenously (i.v., 10⁸particles/100 μl) through intra-tail vein to mice with lung metastases.Four hours later, mice were sacrificed and perfused according to astandard protocol. Lungs were extracted and sectioned on a microtome ata thickness of 20 μm; nuclei were stained with DAPI (300 mM, 5 min). Theimages of lung sections were examined by a confocal fluorescencemicroscopic system ACAS-570 and corresponding filter set, and processedusing ImageJ software.

Therapeutic Efficacy of AA-exoPTX Against Pulmonary Metastases. Theantineoplastic effects of PTX exosome formulation were evaluated in amouse model of pulmonary metastases. To utilize fluorescence imaging,3LL-M27 cells were transduced with lentiviral vectors encoding theoptical reporter mCherry (GBM8FlmC, red) as described earlier (Kim etal., Nanomedicine 12: 655-664 (2016)). To establish pulmonarymetastases, C57BL/6 mice were i.v. injected with 8FlmC-3LL-M27 cancercells (5×10⁶ cells/100 μl/mouse). Forty-eight hours later, mice weretreated i.v. with AA-PEG-exoPTX, or exoPTX, or empty exosomes (exo)(4×10¹¹ particles/100 μl, three times on day 1, 4, and 7; 0.5 mg/kgtotally), or Taxol (same regiment as exosome-based formulations), orsaline as a control (n=7). To assess amount of cancer metastases, twomice from each group were sacrificed on day 16, perfused, and lungslides obtained on microtome (Thermo Scientific) were examined byconfocal microscopy. The rest of the mice (five in each group) weremonitored daily for the signs of the reduced physical activity and theprogression of the tumor. The survive time of each mouse was recorded.

Statistical Analysis. For the all experiments, data are presented as themean±S.E.M. Tests for significant differences between the groups wereperformed using a t-test or one-way ANOVA with multiple comparisons(Fisher's pairwise comparisons) using GraphPad Prism 5.0 (GraphPadsoftware, San Diego, Calif.). A minimum p value of 0.05 was chosen asthe significance level.

Results

Manufacture and Characterization of AA-PEG-exoPTX. As shown in Example2, efficient loading of PTX can be achieved when exosomes are subjectedto ultrasound treatment in the presence of the drug (Kim et al.,Nanomedicine 12: 655-664 (2016)). It is likely that thereorganization/reshuffling of the exosome membranes upon sonicationenabled PTX diffusion across highly impermeable lipid bilayers. Based onthese findings, we applied the same approach for simultaneous loading ofPTX to exosomes along with vectorization to sigma receptor using ananisamide moiety. For this purpose, exosomes were isolated frommacrophages conditioned media, supplemented with varying amounts ofAA-PEG-DSPE lipid and PTX in ethanol solution, and subjected toultrasound treatment as described above. Obtained formulations werepurified from non-incorporated drug on Sepharose 6BCL columns andcharacterized by size, charge, as well as by PTX and protein content.

First, the effect of lipid incorporation on the loading capacity for PTXinto exosomes was evaluated. The amount of PTX loaded into exosomes wasdetermined by HPLC on a Nucleosil C18 reverse phase column, and theloading capacity (LC) was expressed as the amount of the drug vs. theamount of exosomal protein. HPLC analysis revealed that incorporation ofhigh amounts of AA-PEG-DSPE (0.5 mg/ml) into exosomes significantlydecreased their loading capacity (LC) for PTX (FIG. 49A). In contrast,lower amounts of the lipid (0.25-0.05 mg/ml) did not affect LC for PTX.It is likely that excess of hydrophobic chains of the lipid incorporatedinto exosomal membranes diminished available for PTX space. Based onthese findings, the highest amount of the incorporated vector moiety(0.25 mg/ml) that did not significantly reduce PTX loading in exosomeswas selected for all further evaluations. LC for the optimalAA-PEG-exoPTX formulation was ˜33%, comparable to the LC achieved fornon-vectorised exoPTX (FIG. 49A). Noteworthy, ultrasound treatmentsignificantly increased amount of PTX incorporated into exosomes; the LCin exosomes without sonication was as low as 1.4%.

Next, to address a concern about possible alterations in the exosomalmembranes upon sonication, the levels of exosome-specific proteins,TSG101 and flotillin, in different exosomal formulations were examinedby western blot technique (FIG. 49B). The data indicated that the mildsonication utilized for PTX loading with six cycles, and intermediatetime out for cooling down and membrane restoration, did not affect theprotein content of exosomes. In particular, naïve exosomes, as well asboth vectorized and non-vectorized exosomal formulations showed elevatedexpression of exosome-associated proteins (TSG101, and flotillin) ascompared to cell lysate, which displayed greater levels of β-actin (FIG.49B). Noteworthy, all exosomal formulations, as well as parentalmacrophages, were also found to express the lymphocyte functionassociated antigen-1 (LFA-1, subunit CD11a) (FIG. 49B), which assists incell uptake and may bind to endothelial cell adhesion molecules (inparticular, ICAM1) which are overexpressed on activated endothelialcells such as those found in tumors (Maruo et al., International journalof cancer 100: 486-490 (2002)). This is important, since the presence ofLFA-1 on the surface may improve specific targeting of exosome-based PTXformulations to tumors.

Finally, the hydrodynamic size was determined by DLS and NTA (FIG. 49C).Naïve empty exosomes had a narrow size distribution, with an averageparticle diameter of 110.8±4.1 nm and 75.9±2.6 nm as revealed by NTA andDLS, respectively. The sonication procedure significantly increased sizeof exosomes (FIG. 49C). Noteworthy, exosomes sonicated in the presenceof PTX were smaller than those sonicated in the absence of the drug. Wehypothesized that this effect may be due to the stabilization ofexosomal membranes by the incorporated drug. Furthermore, it is knownthat the anionic phospholipid phosphatidylserine is abundant on cellmembranes and contributes to the surface charge of individual cellularmembranes. In this regard, loading of exosomes with PTX did notsignificantly alter the slightly negative change of the nanocarriers(FIG. 49C), suggesting that there were also no major alterations of thelipid content of exosomal membranes. However, the vectorizedAA-PEG-exoPTX formulation was found to have a less negative surfacecharge than exoPTX, probably due to the shielding of the exosomalmembrane by the long PEG chains of the lipid.

Effect of AA-PEG-DSPE Incorporation on Membrane Fluidity in Exosomes.Fluidity of exosomal membrane upon AA-PEG-DSPE incorporation wasexamined using BODIPY-PC. This is a hydrophobic fluorescent compound,which incorporates in the hydrocarbon regions of lipid membranes.Transfer of BODIPY-PC from the aqueous environment into lipid bilayersresults in a drastic increase of the fluorescence emission for thisprobe. Once the probe is incorporated into lipid membranes, itsfluorescence polarization is strongly dependent on the microenvironment,with decreases in membrane microviscosity resulting in increasedfluorescent polarization.

Exosomes labeled with BODIPY-PC were sonicated in the presence ofAA-PEG-DSPE lipid, and fluorescence polarization measurements wererecorded (FIG. 50 ). Co-incubation of PTX with exosomes in the absenceof sonication did not alter membrane microviscosity, although small butstatistically significant fluidization of exosomal membranes wasrecorded when a high amount of lipid (0.5 μg/ml) was added to thesolution. Next, significant decreases (more than two times) in membranemicroviscosity were recorded upon sonication, consistent with ourprevious observations (Haney at al., J Control Release 31; 207:18-30(2015)). The fluidity of exosomal membranes was partially restored whenPTX was added to the solution. Furthermore, sonication of exoPTX in thepresence of the lipid further increased membrane microviscosity up tonaïve non-sonicated exosomes (FIG. 50 ). Noteworthy, the greater amountof lipid was added to the solution; the higher the microviscosity levelsobtained. We hypothesize that sonication leads to dysregulation ofexosomal membranes and the creation of additional space for PTXmolecules. This resulted in an increased LC for PTX. The incorporationof high amounts of lipid molecules upon sonication allowed sealingmembrane bilayers that may impede PTX loading, and as a result, diminishLC (FIG. 49A).

Accumulation of AA-PEGexoPTX in Target Cancer Cells in vitro. Theability to deliver the drug payload into target cells is crucial for thetherapeutic efficacy of exosomal formulations. Although the molecularfunction of sigma receptors is not yet fully defined, there isincreasing evidence that these receptors are overexpressed in manycancer cells (Maruo et al., International journal of cancer 100: 486-490(2002)).

Previously, we demonstrated that accumulation levels offluorescently-labeled exosomes in 3LL-M27 cells was considerably greater(about 30 times) than accumulation of liposomes or polystyrenenanoparticles (Kim et al., Nanomedicine 12: 655-664 (2016)). Here, wecompared the uptake of AA-vectorized exosomes against controlnon-vectorized exosomes. The receptor-mediated accumulation ofDiL-labeled vectorized exosomes (AA-PEG-exo) was studied in target3LL-M27 cells in vitro, and compared to non-vectorized sonicatedexosomes (exo), as well as exosomes with incorporated PEG-DSPE lipidwithout anisamide targeting moiety (PEG-exo) (FIG. 51A). The obtaineddata indicated that vectorized AA-PEG-exo nanocarriers were taken up inmuch higher quantities than non-vectorized sonicated exosomes. ThePEGylated exosomes without AA-targeting moiety were taken up less thanparental exosomes, probably due to the PEG chains blocking interactionof exosomal surface proteins, which assist in cell accumulation.

To further assess the capability of incorporated AA to target exosomesto the sigma receptor, a receptor competitive inhibition study wascarried out in 3LL-M27 cells (FIG. 51B). In this experiment, 3LL-M27cells were pre-treated with free AA at varying concentrations, washedwith PBS, and then equal amounts of vectorized AA-PEG-exo along withfree AA were added to the cells and incubated for one hour. Fluorescencelevels were measured; the amount of exosomes/μg protein was quantifiedand graphed against the concentration of AA (FIG. 51B). Results showed adose-dependent response of AA-PEG-exo to competitive inhibition byincreasing concentrations of free AA, indicating that AA-PEG-exo weretargeted to the sigma receptor and taken up by receptor-mediatedendocytosis. Noteworthy, even a large amount of free AA added to theAA-vectorized exosomes was not able completely inhibit exosome uptake intarget cells, suggesting the involvement of other exosomal surfaceproteins in this process, for example LFA-1 as demonstrated by westernblot.

The importance of exosomal surface proteins in assisting in exosometake-up was confirmed in accumulation studies using proteinase Ktreatment to strip exosomes of surface proteins (FIG. 52 ). In thisexperiment, sonicated AA-vectorized (AA-PEG-exo) and non-vectorizedsonicated exosomes (exo/sonic), as well as non-sonicated naïve exosomes(exo/naive) were labeled with the fluorescent dye DiL, and incubatedwith 3LL-M27 cancer cells for various times. The obtained data indicatethat accumulation levels in target cells increased in order: exo/naïve<exo/sonic <AA-PEG-exo (FIG. 52 ). This confirmed our previous reportsthat treatment with ultrasound improved exosome accumulation in cancercells (Kim et al., Nanomedicine 12: 655-664 (2016)), as well as neuronalPC12 cells (Haney at al., J Control Release 31; 207:18-30 (2015)). Inparallel, the same exosomal formulations were treated with proteinase K,and added to the cells. The digestion of the exosomal surface proteinssignificantly decreased uptake by target cells in all formulations.These results clearly show the advantages of exosome-based drug deliverysystems over common synthetic nanocarriers related to the facilitateduptake of exosome carriers by means of surface adhesive proteins.Noteworthy, stripping of surface proteins from vectorized exosomes(AA-PEG-exo) decreased their transport at significantly lesser extentthan non-vectorized exosomes (FIG. 52 ), probably due to the assistedAA-mediated accumulation in cancer cells.

Effect of AA-vectorization on Intracellular Distribution of Exosomes inCancer Cells. Exosomes are known to function as intracellularmessengers, delivering proteins and nucleic acids (Gyorgy et al., CellMol Life Sci, 68:2667-2688 2011)) from cell to cell. The intracellularfate of exosomes is of the utmost importance if drugs are to bedelivered effectively into target cells. However, the effect ofvectorization with AA on intracellular fate of exosomes and their cargoremains unknown. To assess the intracellular trafficking of exosomes,3LL-M27 cells were incubated with DiL-labeled AA-PEG-exo and exo as acontrol for one hour, and then stained with MitoTracker, or LysoTracker,or ER Tracker dye to visualize mitochondria, lysosomes, or endoplasmicreticulum (ER), respectively (FIG. 53 ). Results showed that exosomespreferentially distribute in order: lysosomes >ER >mitochondria.Confocal images revealed that the intracellular fate of exosomes was notaltered by the addition of a vector to the sigma receptor.

Co-localization of Systemically-administered Exosomes with PulmonaryMetastases in LLC. To assess the ability of AA-vectorized exosomes totarget sigma receptor expressing pulmonary metastases, confocal imageswere conducted in an LLC mouse model. For this purpose, 3LL-M27 cellswere transduced with a lentiviral vector encoding the optical reporterGFP fluorescent protein. To induce metastases, C57BL/6 mice wereinjected with GFP/3LL-M27 (5×10⁶ cells/100 μL) intra-tail vein asdescribed above. 21 days later, autologous non-vectorized (exo) andAA-vectorized (AA-PEG-exo) exosomes were stained with a fluorescent dye,DiD, and administered intravenously (i.v., 10⁸ particles/100 μl) toC57BL/6 mice. Four hours later, mice were sacrificed, perfused; lungswere sectioned on a microtome and examined by confocal microscopy.Nuclei were stained with DAPI.

Confocal images revealed 98.9±0.8% of AA-exosomes (FIG. 54D-54F) wereco-localized with lung metastases indicating efficient targeting ofAA-exoPTX in vivo. In contrast, only 21.8±0.2% of systemically-injectednon-vectorized exosomes were co-localized with cancer metastases (FIG.54A-54C). Noteworthy, no AA-exosomes were found in the lungs of healthyanimals (FIG. 54G-54J). These results suggest thatsystemically-administered exosomes can efficiently reach pulmonarymetastases and deliver their drug payload to target cancer cells.

Therapeutic Efficacy of AA-PEG-exoPTX Against Lung Metastases. C57BL/6mice were i.v. injected with mCherry-3LL-M27 cells transduced withlentiviral vectors encoding the optical reporter mCherry (GBM8FlmC).When metastases were established, mice were systemically injected withAA-PEG-exoPTX or exoPTX (4×10¹¹ particles/100 μl, 3 times on day 1, 4,and 7; 0.5 mg/kg totally), or Taxol (same regimen as AA-PEG-exoPTX), orsaline as a control. 18 days later mice were sacrificed, perfused, andlung slides were examined by confocal microscopy (FIG. 55A). The imagesrevealed a superior antineoplastic efficacy of AA-exoPTX compared tonon-vectorized exoPTX, or Taxol resulting in potent eradication ofpulmonary metastases. The survival studies confirmed these results (FIG.55B). The administration of AA-exoPTX formulation resulted in asignificantly stronger suppression of metastases growth and greatersurvival time in mice with pulmonary metastases. This confirms thesuperior antineoplastic efficacy of AA-PEG-exoPTX upon systemicadministration as compared to Taxol and non-vectorized exoPTXformulation.

Conclusions. The efficient targeted delivery of anticancer agents topulmonary metastases remains one of the greatest challenges for therapy.A common approach for building a drug delivery system is to incorporatethe drug within a nanocarrier that allows higher solubility, metabolicstability, and improved circulation time. Several formulations are beingstudied in clinical trials, or have already been approved by the FDA foruse in humans (Peer et al., Nat Nanotechnol 2:751-760 (2007); Davis etal., Nature, 464:1067-1070 (2010)). However, conventional nanoparticleshave limited biocompatibility, and normally are cleared rapidly from thecirculation by the MPS (Peng et al., Biomaterials 34(33):8521-30(2013)). This example presents a new drug delivery system that is basedon natural vectors, exosomes, released by autologous macrophages for thedelivery of a biological agent exemplified here by PTX. Exosomes play asignificant and diverse role in intercellular communication that is anessential process for the development and function of multicellularorganisms. In this regard, we utilize macrophage-derived exosomes thatexert unique biological activity reflective of their origin and canprovide advantages of both cell-mediated drug delivery that based oninnate functions of immune cells and nanotechnology.

Using exosomes as drug delivery vehicles offers a number of benefitsover common drug administration regimens; however, there are somelimitations and challenges that need to be addressed. One of the majorchallenges is the efficient loading of exosomes without significantchanges in the structure and content of exosomal membranes. PTX is ahighly hydrophobic compound that is likely to be incorporated into thehydrophobic inner region of the relatively tight and highly structuredlipid bilayers of exosomes. Therefore, we developed a specific procedurewhen lipid bilayers were reshuffled upon mild sonication withoutsignificant alterations of protein and lipid content. To target exosomalcarriers to cancer cells, we also incorporated a vector moiety withanisamide that is known to specifically bind sigma receptoroverexpressed on many cancer cells using the same sonication procedure.Using mild sonication of exosomes in the presence of PTX and anisamidevector we optimized the amount of incorporated vector moiety to thelevels which allow high loading capacity for the drug. The obtainedAA-PEG-exoPTX formulation showed an extraordinary ability to accumulatein target cancer cells; these exosomes were taken up viareceptor-mediated endocytosis in considerably greater numbers thannon-vectorized exosomes in vitro. Noteworthy, vectorization withanisamide did not alter intracellular trafficking of exosomalformulations in cancer cells.

The most interesting results were obtained in the mouse LLC model. Ourdata demonstrate a robust accumulation and nearly completeco-localization of systemically administered AA-vectorized exosomes withcancer cells. We hypothesized that both AA-vector along with LFA-1protein expressed on exosomal membranes were responsible for thispreferential accumulation in pulmonary metastases upon systemicadministration. Significantly, exosomes were targeted to livermetastases as well; a complete co-localization of AA-vectorized exosomeswith cancer cells was demonstrated in this work.

It is likely that the efficient targeted delivery of PTX incorporatedinto AA-vectorized exosomes resulted in superior inhibition of pulmonarymetastases growth in the LLC mouse model compared to exoPTX or Taxol.Significantly, LLC cells are known to express Pgp drug effluxtransporter in vivo (Batrakova et al., J Control Release 143: 290-301(2010)). We demonstrated earlier that the incorporation of PTX intoexosomes may not only increase its solubility, but also allow forovercoming Pgp-mediated drug efflux in the resistant cancer cells. Thiseffect may be attributed to the difference in route of internalizationof exoPTX, as compared to Taxol. Exosomes and micelles, such as thosefound in Taxol, are taken up by endocytosis, but exosomes have superioruptake due to the presence of adhesion proteins, tetraspanins,integrins, immunoglobulins, proteoglycans, and lectins (Mulcahy et al.,J Extracell Vesicles 4; 3 (2014)), which are not found on artificialnanoparticles. Furthermore, exosomes consist of cellular membranes thatmay fuse with the plasma and/or endocytic membranes and deliver theircargo, bypassing Pgp-mediated efflux.

Moreover, it is known that exosome-mediated cell-to-cell communicationis key in the battle between cancer and the immune system (Finn et al.,Ann Oncol 23 Suppl 8: viii6-9 (2012)). Thus, Parolini et al. (Paroliniet al., J Biol Chem 284: 34211-34222 (2009)) showed that exosome fusionwith target cells occurs more efficiently under acidic conditions,implying that exosomes may be taken up preferentially by tumors (whichhave an acidic microenvironment) rather than the surrounding healthytissue. Finally, decoration of exosomes with PEG chains maysignificantly increase their circulation in the blood as wasdemonstrated earlier (Kooijmans et al., J Control Release 224: 77-85(2016)). Without limiting our invention to a specific theory, all fourmechanisms mentioned here are likely to have significant impact onAA-PEG-exoPTX anticancer activity, i.e.: (i) vector-mediatedpreferential accumulation in cancer cells, (ii) efficient delivery ofincorporated cargo into target cancer cells, (iii) by-passingPgp-mediated drug efflux in resistant cancer cells, and (iv) prolongedcirculation time in the blood. Indeed, further investigations arenecessary to uncover this mechanism. Overall, macrophage-derivedexosomes allow harnessing the innate biology of immune cells andcombining these advantages with nanotechnology. Thus, exosomes promisean unparalleled efficacy in the treatment of many life-threateningconditions, including those lacking effective pharmacotherapy.

Example 12 Preparation of Exosomes Loaded with Small Molecule BiologicalAgents Using Poly(2-oxazoline) Polymeric Micelles

Poly(2-oxazoline) micelles loaded with single drug or multiple drugswere prepared via the thin film hydration method (Luxenhofer et al.,Biomaterials 31(18):4972 (2010)). Briefly, predetermined amounts ofpolymer and drugs were solubilized in an organic solvent (e.g., acetone,acetonitrile, and ethanol) and mixed together. The organic solvent wasthen removed under a stream of nitrogen gas or air (40° C.) to produce athin film of intrinsically mixed drug-polymer blend. In order tocompletely remove the residual solvents and obtain dry film, the filmswere deposited in the vacuum chamber (approx. 0.2 mbar) overnight.Subsequently, the formed thin films were rehydrated with the desiredamounts of aqueous saline or bi-distilled water and then solubilized ateither room temperature or upon heating at 50-60° C. for 5-20 minutes toproduce drug loaded polymeric micelle solutions. The rehydration timewas dependent on either the drug concentration or the composition of thedrugs or the multi-drug mixtures. The polymeric micelles loaded with thesingle drug were prepared accordingly with the final polymerconcentration of 10 g/L and each drug feed concentration of 2 g/L, 4g/L, 8 g/L, 10 g/L and 12 g/L. The polymeric micelles co-loaded withmultiple drugs were prepared using the same final polymer concentration(10 g/L) and predetermined concentrations of each drug component ofmultiple drug mixtures. The aqueous polymeric micelle formulation wascentrifuged at 10,000 rpm for 3 minutes to precipitate non-dissolveddrugs or drug-polymer aggregates. A triblock copolymer ofpoly(2-butyl-2-oxazoline) (PBuOx) as the hydrophobic block andpoly(2-methyl-2-oxazoline) (PMeOx) as the hydrophilic block havingPMeOx-b-PBuOx-b-PMeOx structure was used as the polymer. The length ofthe PBuOx block ranged from about 10 to 30 repeating units (r.u.) whilethe length of each PMeOx block ranged from about 30 to about 50 r.u. andthis variation did not affect the solubilization results.

The following small molecule biological agents were used to preparesingle drug micelles or multiple drug micelles: an ATM (Ataxiatelangiectasia mutated) kinase inhibitor KU55933, cytoskeletal drugsthat target tubulin—paclitaxel (PTX) and docetaxel (DTX), ATM/ATR(ataxia telangiectasia and Rad3-related protein) inhibitor VE-822, Bcl-2family protein inhibitors ABT-263 (Navitoclax), PI3K/AKT (Protein kinaseB) inhibitors AZD5363 and LY294002 and LY294002 hydrochloride, a checkpoint inhibitor AZD7762, an Mtor (mechanistic target of rapamycin)inhibitor AZD8055, a topoisomerase II inhibitor etoposide (ETO) orVP-16, a proteasome inhibitor LDN-57444, topoisomerase II inhibitorspodophyllotoxin (PPT), otherwise known as podofilox and teniposide, abioflavonoid rutin, a synthetic retinoic acid receptor a (RARα) agonist,tamibarotene, an antagonist of aldosterone spironolactone, a3-hydroxy-3-methylglutaryl (HMG) coenzyme A reductase inhibitorsimvastatin, third generation taxoids SB-T-1213, SB-T-121302,SB-T-121303, SB-T-1214, SB-T-121402, SB-T-1216 and SB-T-121602 (He etal., J. Control. Release 208:67 (2015)), a vitamin D2 ergocalciferol, athird generation retinoid bexarotene (Schulz et al., Polymer Preprints53(1):354 (2012)), a proteasome inhibitor bortezomib (BTZ) and Hsp90inhibitor 17-N-allylamino-17-demethoxygeldanamycin (17-AAG) (Han et al.,Mol. Pharm 9(8): 2302 (2012)). All of these APIs have very low (lessthan about 0.1 μg/mL) or low (from about 0.1 to about 1 μg/mL)solubility.

As the next step the IC21 macrophages are treated with the obtainedpolymeric micelle solutions. Briefly, macrophages grown in T-75 flasks(15×10⁶ cells/flask) are incubated with the polymeric micellescontaining biological agents obtained as described above in serum freemedia for 2 hours to 96 hours. In each case the duration of exposure ofthe cells with the polymeric micelle solutions is adjusted to ensurethat the cytotoxic effect on the donor cells is minimal. In selectedcases the donor cells are additionally incubated with 0.5% Pluronic® P85solution for four hours. Following the incubation, the cells are washed3×PBS, and cultured in serum-free media for another 20 hours. Followingthe incubation, exosomes are harvested from the macrophages media usingthe ExoQuick-TC™ Kit (System BioSciences; Mountain View, Calif.) andwashed twice with PBS. The recovery of exosomes is determined bymeasuring the protein concentration using the Bradford assay and by NTA.The amount of biological agents incorporated in exosomes is quantifiedvia reverse-phase high performance liquid chromatography (HPLC).

Example 13 Preparation of Exosomes Loaded with Small Molecule BiologicalAgents Using Pluronic Polymeric Micelles

Pluronic® polymeric micelles loaded with drugs were prepared via thethin film hydration method as described in Example 12. A triblockcopolymer of PEO-PPO-PEO Pluronic® F127 was used as the polymer. Thefollowing small molecule biological agents were used to prepare singledrug-containing polymeric micelles: doxorubicin, epirubicin,daunorubicin, vinblastine, mitoxantrone, camptothecin, and SN-38. As thenext step the IC21 macrophages are treated with the obtained polymericmicelle solutions as described in Example 12. In selected cases thedonor cells are additionally incubated with 0.5% Pluronic® P85 solutionfor four hours. Following the incubation, the cells are washed 3×PBS,and cultured in serum-free media for another 20 hours. Exosomes werecollected by PEG precipitation from macrophage concomitant media and thenumber of particles was accessed by NTA. The amount of biological agentsincorporated in exosomes is quantified by HPLC.

The foregoing is illustrative of the present invention, and is not to beconstrued as limiting thereof. The invention is defined by the followingclaims, with equivalents of the claims to be included therein.

1-72. (canceled)
 73. A composition for delivery of a biological agent to a cell, the composition comprising an exosome comprising the biological agent, wherein the biological agent is not naturally present in the exosome and is an enzyme.
 74. The composition of claim 73, wherein the exosome is isolated from a macrophage/monocyte.
 75. The composition of claim 73, wherein the enzyme is an enzyme associated with a lysosomal storage disorder (LSD).
 76. The composition of claim 75, wherein the enzyme associated with an LSD is lysosome-associated membrane protein 2 (Lamp2b), acid α-glucosidase (GAA), acid sphingomyelinase, iduronate-2-sulfatase (I2S), α-L-iduronidase (IDU), β-hexosaminidase A (HexA), acid β-glucocerebrosidase, N-acetylgalactosamine-4-sulfatase, or α-galactosidase A.
 77. The composition of claim 73, wherein the exosome further comprises a targeting agent.
 78. The composition of claim 77, wherein the targeting agent is attached to the surface of the exosome.
 79. The composition of claim 78, wherein the targeting agent is attached using a polymeric linker.
 80. The composition of claim 79, wherein the polymer linker is a water soluble polymer linker.
 81. The composition of claim 79, wherein the targeting agent or polymeric linker is connected to a lipid group in or on the exosome.
 82. The composition of claim 73, wherein the exosome is modified with a molecule containing multiple charges.
 83. The composition of claim 82, wherein the molecule containing multiple charges is a polyion or a lipid.
 84. The composition of claim 73, further comprising a pharmaceutically acceptable carrier.
 85. A method of delivering a biological agent to a subject, across the blood brain barrier of a subject, or to inflamed tissue of a subject, comprising delivering the composition of claim 73 to the subject, thereby delivering the biological agent to the subject.
 86. A method of treating a lysosomal storage disease (LSD) in a subject in need thereof, comprising delivering a therapeutically effective amount of the composition of claim 75 to the subject, wherein the biological agent is effective for treating of the LSD, thereby treating the LSD in the subject.
 87. The method of claim 86, wherein the LSD is Gaucher's disease, Pompe disease, Niemann-Pick, Hunter syndrome (MPS II), Mucopolysaccharidosis I (MPS I), GM2-gangliosidoses, Gaucher disease, Sanfilippo syndrome (MPS IIIA), Tay-Sachs disease, Sandhoff's disease, Krabbe's disease, metachromatic leukodystrophy, or Fabry disease.
 88. The method of claim 86, wherein the enzyme associated with an LSD is lysosome-associated membrane protein 2 (Lamp2b), acid α-glucosidase (GAA), acid sphingomyelinase, iduronate-2-sulfatase (I2S), α-L-iduronidase (IDU), β-hexosaminidase A (HexA), acid β-glucocerebrosidase, N-acetylgalactosamine-4-sulfatase, or α-galactosidase A. 